would it be better to get an fi q (1000 rms) or an ascendant audio chaos 12 (800 rms). which one would be better on this power or would they be equal for my mtx 801d?
If your goal was obvious, two people would not be asking you questions to help you find the right direction to go. Are there space limitations that might force you to go sealed? Are you worried about budget between the two? Did you prefer a certain enclosure? Is sheer out put or flat response your preference? etc etc.
if it were me id look for a bigger amp. ive found its nice to have about %50 extra power than your subs need. Keeps things distortion free and will make your subs happy.
a lot of subs can take much more than rated power if its clean unclipped power. i ran my infinities kappa perfects at double rated and they absolutely loved it . My 2000 rms alpha loves 3k and my 1000 rms sx liked around 1300. a fiend of mine is even running his shitty pioneers on double rated power, they complain a bit tho but still they suck and they take it.