Pocket friendly and 500 rms ? hmmf. see if you can find a phoenix gold TI or ZPA on like ebay or some shop that isn't out of them. i think Zapco are good quality too but i've never bumped one of those .
http://www.phoenixgold.com/2004/titaniumamps.html
none of that is really pocket friendly though ... :\
these are priced okay
http://www.phoenixgold.com/2004/rsdamps.html
Maybe go Dual 4ohms , and find a mono block stable @ 2 ohms
that amp is 600 RMS @ 2 ohms ,

good 2 go
http://www.bestwebbuys.com/electroni...?isrc=e-search
http://focuscamera.com/prods/964698140.asp
600 RMS at 2 ohm. how good are those speakers ?
if the sub says 500 peak, get the next sub down