One thing to keep in mind about power to a CS-Plus is that the sweet spot is right around 350 to 550 watts. Obviously the use of a subsonic filter (or not) is just one of the many variables here.
You could have a kilowatt hooked up and not have a problem as long as the sub was properly set up in a typical room (the extra amp power would just never be used) so bridging or not bridging shouldn't bother you.
In the end, you will get FAR more utility (say for those large rooms) if you added a second CS-Plus as opposed to jumping from 400 watts to 800 watts powering one. Based on what is mentioned above about this amp's power I'd probably run it not bridged. Trying it both ways is always advised, just make sure you use a SPL meter and a test disk to calibrate.
It wouldn't be hard to smoke a woofer with 900 watts (and no subsonic filter) that was calibrated "by ear".