I've worked in with insurance for approx 6 years now. Under your own collision or comprehensive coverage you are typically provided $1k of aftermarket parts or equipment coverage w/ the basic policy (this may vary depending on your insurance company and the state you live in but it is pretty much the norm). You may add additional aftermarket parts coverage (referred to as custom parts and equipment) in different amounts. The aftermarket parts have to be permanently attached to your vehicle for coverage to apply (ie the subwoofers sitting in the cargo area or the 100+ case of CD's that are not permanently affixed to your X will not be covered.) If the insurance company is replacing an aftermarket part they will pay $ for $ pending you have evidence of the cost of that part up to the $ maximum of your a/m coverage.

Now for a kicker for those of you that have lots of $ into your X even if you purchase additional a/m parts coverage on your policy & your vehicle is a total loss you will not get $ for $ on the a/m equipment. The insurance company will run an evalution on whether or not the a/m part increases value to your vehicle. For the most part the insurance company will argue in the instance of a suspension lift, larger tires, etc that it does not increase the value of the vehicle to the general public so you may not receive any additional money from the base price of the vehicle.

If your vehicle is hit by someone else these rules do not apply to you and you would be covered up to the policy limits of the at fault party. (in CO the minimum limit of liability is $15k, which is way too low).

To answer one of the earlier questions if you have your bikes on a hitch mounted rack & you are rear ended the other person's insurance company will pay for the bikes, hitch carrier and vehicle damage. If you back into something w/ your bikes your policy will not cover the bikes & may or may not cover the hitch carrier but would cover the vehicle damages. Damn I'm winded