Bestbuy is not totally out of the question..That is if you can get your hands on employee discount/ don't want an entire system..However if you can get your hands on the employee discount (which is pretty big in car audio due to the markup) I would get 2 Alpine Type-R 12"s.. (the only subs i would buy there) Now there 220 each..but you can get them for 110 a piece.. so thats 220 for 2..then buy a amp wiring kit, again if you have discount a 4 gauge should run about 35 dollars..Now for the wood for the box..3/4" MDF $25ish..then some GE silicone 2.. it shud be about 7 bucks and 1 shud do..now find someone or build it yourself..now thats 220+35+35= 290..that leaves u 210 for a amp..id suggest looking in the classified section here and finding a nice used amp..i think the only type-rs they carry at bestbuy now are dual 4 ohm..so 2 = 1ohm or 4ohm load..now with an rms of 500 i dont think a used 1000watt@1ohm amp will be hard to find..however you still wont have a headunit, front stage, or upgraded electrical so u just purchased 1/3 of a system for 500$..save up and add the rest..hope that helped you gl man