Your dillema is a little confusing to me. Is your amp a mono block amp or is it a 2 channel amp? Your amps provide 500 watts at 4 ohms right? Is that 4ohms bridged or stereo? Is that amp stable at 2 ohms? I am going to assume yes, so this should be your wiring: Bridge each amp to one voice coil of one sub. This will give you a 2 ohm load (or 4ohms bridged) on the amp which=more power. If it is a 2 channel amp then you could wire each channel to each voice coil of the sub for a 4 ohm stereo load, but then again, why would you want to? Also to clear up some confusion, 4 ohm speakers will always be 4 ohms while you can wire the 4 ohm subs to 'trick' the amplifier into seeing a different ohm load.
