Pay particular attention to the impedance of your system, and that which your amp can handle. Wiring in parallel will bring your overall impedance down to 2 ohms (and allow you to run a mono amp or a 2 channel amp in bridged mode)...you need to make sure your amp can handle that. On the other hand, wiring in series will push you up to 8 ohms, which will rob you of available power (not the best terms to describe it, but basically you won't be taking advantage of what the amp can offer). Wiring into a 2 channel is an option, though I've personally never seen the point (unless we're talking about speakers). But again, gotta pay attention to the impedance.
JVC Arsenal KS-AR8002D 2-channel car amplifier 150 watts RMS x 2 at Crutchfield Signature
would work well wired as 2 channels.
Rockford Fosgate Punch P300-1 Mono subwoofer amplifier 300 watts RMS x 1 at 2 ohms at Crutchfield Signature
would work if you wired your subs in parallel.
Thats not even getting into quality, but should at least help you to eliminate amps that won't work.