Are your subs 2ohm or 4ohm each? That makes all the difference in what amp you want to get.
500Wx1@4ohm is effectively the same as 250Wx2@4ohm. However if your amps are 4ohm each, run them in 2ohm configuration as most monoblocks are more efficient with 2 ohm delivery.
Actually you will want to get a monoblock for the reason that TRUE monoblocks (class D amps) are very power efficient - they use about 70% power (the rest goes to heat) as opposed to 40-50% of regular (class A/B) amps. That will help with headlight dimming problems and the like.
Brands, it's all personal preference. Alpine are always nice but they aren't cheap.
Im running an Audison (Italian made) amp, I'm more into SQ than doof-doof. I like the MB Quart amps (beware, apparently there are fake MB Quart amps on eBay!), if you want to s tay American you can go JL Audio or Soundstream as they both make awesome stuff.
Don't like Fusion tho.