Option Audio are pretty good for the money, and definately on of the better choices when on a budget.
You can run as many subs as you want off a mono block, provided you match the impednce levels. Mono blocks are designed to put out more power at a lower impedance which is why they are more suited to subwoofer applications. If you look at the specs of the amps, you will see the power output varies at different impedance levels. You will see it as "ohm" if your not sure.
I'm not familiar with your sub, but i think Acarmody had a guess above saying the they are a single voice coil 4 ohm. So any amp that produces good power at 2 ohm is what you will be after. (best just post the model numbers though of the subs to be %100 sure)
Depending on the voice coil arrangement of the subs, will determine how they can be wired and what impedance load they will put to the amp.
Basically wiring in parralel will have the load, wiring in series will double it.
If you jump on google and search a few key words like parralel and series wiring, and subwoofers, you will see a heap of results. I won't link you to any specific one as there are probably better one's worth reading.
