ebay is a reasonable site. but its a deep buyer beware regardless.
i ordered plently car audio eqiupment their and has never failed on me. of course, ordered as new. their were 1 seller (finestdeals) that sent me an DOA and seller (kruzinaudio) that sent me a wrong box mistakenly, but that was taken care of.
if its a power seller, i tend to avoid if he or she has more than 3 negative feedbacks per month. if its just a private seller, i keep my limit as 1 negative and of course, i would have to read onto it.
as for warranty, you can forget about it. everything is basically "as is" once you sign for that package at the door.
i've bought my amp, all my wiring, my iva-310, and countless other things on ebay and never had a problem. just make sure they are reputable, and it never hurts to check here to see if anyone else has delt with them
There are someebay sellers that offer manufacturer warranty. They are never as long of a warranty as you would get at your local dealer.....typically only 90 days. But sellers like TheStereoDirect (Mitek), highdesertaudio (RF), TeamCSW (DEI) and sell2all (Kicker) are extremely reliable and are basically factory outlet stores for overstock or refurbs for the companies I listed in parenthesis.
No, not all the time. But it helps to be able to see buyers feedback on the seller and see how other refs went. The place I bought my subs from had sold over 25,000 items with great feedback. I got my subs when told and exactly how described, brand new in box. But ebay has its pros and cons.