500 watts a piece, so your going to want some thing in the area of 1000 watts RMS, at whatever ohm you cant wire those things for.
As Bronx said, let us know what voice coil configuration those subs are and we can help you out a little more.
Here are some wiring options depending on VC config. (with two subs):
SVC 4 ohm-2 ohm final load
SVC 2 ohm-1 or 4 ohm final load
DVC 4 ohm-1 or 4 ohm final load
DVC 2 ohm-.5 or 2 ohm final load
So, say those subs are DVC 4 ohm, you can wire them for a final load of 1 or 4 ohm, so you would need an amp that does around 1000 watts RMS at either 1 or 4 ohm.
Troyer Tuned-3.5" AF1-Magnaflow SI/DO
Eclipse CD 8053
Rainbow Profi Vandis, active
Arc Audio 4050XXK
15" SI Mag, 2.5 sealed
Arc Audio 1500XXK