I would suggest a mono amp. If you buy a two channel amp you will have one sub on each channel (4 ohm load), or will have to bridge it to run the subs at a lower ohm load, which it might not handle. However, if you could purchase subs that are DVC, you could parallel wire each coil of each sub (2)onto each channel of the two channel amp, for a two ohm load, and will pound the subs.
would a Kenwood KAC-8151D 200W x 1 Mono Subwoofer Amp be sufficient to power both the mtx subs
Should be fine, I looked it up and it was rated at 400W RMS at 2 Ohms. It was a Class D amp, with remote Bass Boast and infrasonic filtering. So yes, if you wire the two MTX's in parallel, +2+,-2-, you will have a two ohm load, and should be able to tailor the amps infrasonic filtering and bass boost to your liking. It was listed at around $350.00, for which you could look on the forum for a used amp that puts out more power, I think I saw a 600.1 on sale earlier.