Can we focus on what the OP needs pretty please? 

Nice find on the MMATS amp, I appreciate them simply for the fact they are made here in the USA.  We carried MMATS for a short bit.  As for the question at hand, I am a little unsure due to the topic getting a little convoluted.  Are you looking to go with a pair of HDS210's for a nice budget install or is sheer output per dollar the goal?

Well I just got two 10" hds200 and using a mtx thunder1501d and I've tuned and yeh its got louder now but I'm guessing it may be high 130s touching 140db but I'd like to change to set of 12s and want them to hit hard hard and go little lower then the f/s 37 on hds200. I'd even change amp to a sq3500 or like so I could at least double my power ,just want more air and hit most notes I listen to..hip-hop and decafe stuff. I doubt I'll keep the mats since power wise isn't enough 

Subs play lower then their fs, what does your enlosure look like as it could be the culprit.

so box is port up and subs up with port almost in between from seats alignment wise , 2" wide portx13" deep and interior box space before port for two 10s is 3.14cubic ft and port isnt designed like the kerf style just a slot port double 3/4 baffle and shared chamber