If you get a 2 channel amp, It must be able to handle .5 ohm stereo loads in order to handle 1 ohm mono loads when bridged. There are a few amps that can do this but not to many. You can probably find a mono amp that is 1 ohm stable.
You could buy 3 mono amps, 1 for each sub. Next time buy DVC subs so you have more wiring options.