You can only use the CA-DA12250 if you wire each subs VCs in series so each sub has a total impedance of 4 ohms, as it's only stable from 4 ohms... 440W RMS x 2 @ 4Ω Bridged. It's a workable solution but not really the preferred one.
A better solution if you can't find a Fusion monoblock to power both at once is to buy 2 monoblocks... saves bridging. The CA-AM10900 will do 480W RMS x 1 @ 2Ω.
I would prefer 1 (or even better 2) of the CA-DA12250 as they have plenty of power and allow you to wire your VCs up in whatever configuration you like really.
"You double the distortion (0.5% THD suddenly becomes 1.0% THD) and you quadruple the noise floor (raise noise by 6dB). You also cut the damping in half. "
Also an extract from 'Audio Asylum - Biamplification Basics'
Bridging (also called monobridging or monoblocking) is the summing of two channels of an amp to give one higher-powered channel. An amp normally rated at 100W might deliver 300W to 400W when bridged. Because of the summing however, the load on the amp is seen as half of its normal value. In other words, an 8-ohm speaker becomes a 4-ohm speaker load, and a 4-ohm speaker becomes a 2-ohm speaker load. Speaker impedance ratings are nominal only. Actual impedance may dip to a much lower value through part of its range. When an amp's current load has been doubled due to bridging, it can often fail to provide the required amount of current into the load. Sonic effects include harshness in the midrange and highs, and thin bass. In almost all situations therefore, biamping with similar amps will result in better sound quality than bridging. Bridging is best left to professional sound-reinforcement applications, where sound quality is secondary.
I tested this in my old system, going from a bridged setup to a monoblock and there was a definite improvement.
If you are investing this much time and money into a show type install, don't cut corners on the sound gear, you will regret it!