New to site and need some help with sub choice. I just bought a '08 Silverado Crew Cab with a SubThump single 12" sealed box and currently has a Kenwood KFC-W3012 in it and I am definitely not happy with it. I have a hair less than 6.75" of mounting depth and .95 air space before sub and it doesnt have any filler but could get some if need be. To power it i have a 600w Infinity Ref mono block. I also have ID CTX65 Components and a Pioneer 4200dvd deck and listen to everything....I would say rock and rap more than anything else. I am more into SQ but want something that can hit low and fast and sound great doing it. Budget wise I would like to stay under $300. So.....what do you all think would work great for me? Anything I forgot to mention?

Look for a few 8" subs, like DD 9512, JL 8w7, TREO SSi8. A single 8 from these will do. You can make a baffle to fit over the 12" opening and put the 8" sub in there. At that air space you could even port it for an 8". TREO's TSX line would do good in that size box too.

Sundown SA-8 beefy little subs

you could look into a SSA ICON or DCON .95 is a hair small for either but i think you would be happy. Check above in the SSA store and shop around