i don't know about other people, but when i was shopping for my xterra i spent lots of time searching the internet (and of course the nissan site) and looked at every detail myself. the searching and reading itself was interesting to me, because it was my future ride. but i guess that's just me.
to answer your question, a v6 is a definite. i can't imagine the xterra in a 4 cylinder. then after that is 4wd (which is only available with the v6). typically xterras you see on the lot will have the floor mats, onboard airfilter, body moldings and the tow hitch (all of which you get charged extra for).
the power package is another convenient one, since the xterra is a 4 door and allows you to control everything from the driver's seat.
simply put, get the v6 and 4x4. then the power package if you're lazy (like me).