i dont know about the MTX, but i do know that the kicker will perform very well and that it is rated at a 12 volt system, meaning that the amp will do 600 without the car started, and about 700-800 watts when the cars started. i know this only because i have the kicker kx1200.1 and it does 1500 watts. so if i had to choose i would go with kicker because i have had little experience with mtx.
the 801d is now last yrs model and if it messes up, you have to send it back to mtx for repairs and wait 3-5 to get something back. (so ive heard) i dont know if you would want to go through that. but it is a very good amp