First this is not worth reading if you are not going to do it. Just look at the pictures!
Below links.
I did this will all parts I had laying around the garage, I only had to buy the converter harness to go from factory plugs to wires for head unit. If you are just looking click on picture links.

Start to finish for experience installer is about 8 hours, Cost was less than Factory RF Option. Bonus was name brand you choose components! Or dig out of stock heh heh!

I have an s model 2005 xterra, objective 1580 watts, 1 10" Sub in RR, Double Din Head unit, Amps in floor in back, upgrade speakers, maintain factory look and inconspicuous appearance so thieves don't gank my ship, And bolt it down with all security screws so if they do try to steal it, it won't be worth anything to them either. I'm maintaining a conservative look. But I can feel the music! It sounds much better than factory RF system, (sorry Guys)

Get the head unit out.
The tray above it pull straight up, Clips are on the sides, use a very small flat screwdriver. Best to start at FR side as you sit in vehicle.
Get that out, There is one screw in center just below it. Remove.
Now the whole center panel comes out. Just carefully pull straight back.
Undo all the wires because if ya let it hang a clip will scratch the dash at bottom.

Stereo is held in with 4 very visible screws. Brackets on stereo easily transfer to a new Double Din Unit and likewise probably a single din.
Speaker wires can be used for an aftermarket install saving you the hassle of running new ones, Use a battery to test the leads before you unhook old speakers. You can obtain aftermarket wire harness converter that keeps all factory plugs unharmed. The colors are different from radio end to speaker end so you have to test them out.

Door panels are all the same. Proceed as follows.
On either side of the handle that you pull on are small panels. These lift straight up and off. I used a sturdy putty knife, and a small flat driver.
At the handle (Latch) that you use to open the door, the chrome one, each side of that circular part pulls straight out, I used a small flat screwdriver. Once you have these 4 parts out, Also lift out and unplug power window panel. then you will see screws 10 mm or cross or flat takes them out.
Now use a putty knife and get under panel at bottom (In case you scratch no one sees it) put knife in and pull towards you to dislodge the clips, once you get em started you can do it by hand. Panel lifts directly up up up. Use no outward pressure. Your speakers are now exposed. 6X9 in front and an integrated 6.5 in the rear. Front is a direct replacement. I had to have an adapter plate to install the rear since it was some sort of wierdo factory deal. There is room in there for 6X9's also if someone wants to do some fab, it can be done. I just wired regular speaker leads into factory wires so as not to ruin the clip in case I return the system to factory. Install panels in reverse order. Actually pretty easy, but note that the clips are very strong, it almost feels like you are going to break them when you are taking them out. Be easy, use broad tools when you can. If you are chicken mask off where you pry.

I used the rear floor compartment for both amps. (barely fit) I can install a Fan but I am listening to my unit, not playing it for the people 9 cars over ....just 4. So Heat should not be an issue. If it is, I have a 12 V fan ready to cool things down. After testing I know no fan will be needed. I'm cool. Notice in Pic one slants, allows extra air circulation.

The sub is a custom box in RR area, Dealer said ok to use it, just leave room for air to pass to the area when heater is on recalculate it draws air through that panel. Let it breath. I maintain ability for the roller cover to be drawn over everything so when parked I can hide the sub. Some aftermarket Subs were available. But I did not like the location. You hardly notice it where it is at. It is also covered in Vinyl so as to keep with the Xterra theme,,,,, everything you need, nothing you don't. Mark said traditional speaker carpet looks tacky. Mark was right. It looks great!

After all this it's just a matter of run the wires hook them up and tune it all.
Manual points out don't connect directly to battery because Alt will not "Read" the load and thus not keep the Batt fully charged. They give you plenty of places at the Battery to hook pos after the fuse, do that and ground to nearby frame location.

My wires to rear amps are run from Bat, Back to firewall Over to Driver side and in at the boot behind and below brake reservoir. Then they follow the natural path of under the kick panels and carpet on the driver side to the rear cargo area. Speaker wires from amps were run on pass side to back of head unit.

All I had left over was 4 Speakers intact and a head unit. On the shelf!

photo1: Sub in Rear Vinyl finish, Sounds great! Notice cover still functions. No Cheap blk/gry carpet look, wipes clean. with Bass set to zero I almost have too much!
http://www.ssb5.net/users/15670/100_2059.jpg
photo2: This is a Panel that slides into Cd slot Hides Head unit.
easy to make with project box from RadioCrap. (shack)
http://www.ssb5.net/users/15670/100_2061.jpg
photo3: These are the Amps, 1 1000 1 400 Head unit is 180 (on tap)
http://www.ssb5.net/users/15670/100_2063.jpg
photo4: VA XC on face of head untt! Programable, Cool eh? Notice plays CD, Cassette, and has Aux in to play anything with a headphone jack!
http://www.ssb5.net/users/15670/100_2064.jpg
photo5: Anothe head unit shot. I got this unit 80% off, I have 2.
http://www.ssb5.net/users/15670/100_2065.jpg
photo6: Close of of anti theft cover, no see no steal. I hate theives!
http://www.ssb5.net/users/15670/100_2067.jpg
photo7: Where I put my XM, The newer Roady is in the works, will fit better no wires showing.
http://www.ssb5.net/users/15670/100_2068.jpg
photo8: Key Mod, Anti Theft Key blocker. (Home made.)

Make your own, spray cap, clay type JB weld, spare key you get the idea. I left this at dealer and they called me to ask what to do to start it. LOL It freeks everyone out.

http://www.ssb5.net/users/15670/100_2069.jpg

Any questions fee free.

Happy Trails!
MC
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My Standards SET Standards.-05 "S" X Silver-Garmin 188C and Garmin 60CS GPS- 1580 Watts of JVC/Alpine sound with XM - Shrockworks Sliders - 60" High Lift jack - Black Truck Bed Painted undercarriage - Aux Alarm System, CB and Ant! .....More to come.

WOW,, to much reading for me LOL

usmc, can you go into more detail about the anti theft key mod. Spray cap? does this mean spray paint cap? clay type JB weld? not a welder, sorry.

yea, i'd like to know more about that anti-theft device of yours. haha. so confusing but looks cool.

Too much detail or not enough I an't win. Yep, a spray cap. Find one that just covers key cylinder, then cut the inside ring so that when key is turned to start it has some back presure, Then fill it with JB weld, The kind you knead not mix. Then stuff it around your key, put it in the lock for alignment, make sure it turns so you have right depth, carefuly remove it and then allow it to dry, Now when you put it in it looks like mine does. Make one with a cut key and one with a blank, Blank one is added security measure. Crooks think it's some new type lock. The Nissan logo is from a key ring cut to fit. It's fun to have.

I have a question about where you hooked up power wire for your amps. The 2 fuses are 140A and some other lower number for the main cables coming off the battery I think that attaching after that point would be a bad idea. Nissan fused those wires at those amperages for a reason and if you are adding more load, more amps, that fuse will blow. I am not disputing the fact that the alternator will not charge correctly if hooked directly to the battery, but it doesn't make sense.

The only reason I bring this up is beacause I have been looking for the correct way to hook to the stock battery. A standard ring terminal seems fine, but I prefer a "beefier" mount.

If anyone has insight or ideas it would be appreciated!

Thanks