Ok, Im wanting to keep my stock head unit for a bit...mostly budget wise, and hell, its got a warranty. So, im looking at a sub box on eBay with two Xtant 405s(i know these arent great, but they are free). I am curious if an amp is put in, would the stock head unit give any support to the subs? I know to do it right i need a cap, other speakers and lots of goodies...but im looking to go in stages...any ideas? thanks!