I'm confused, you're asking for a lot of stuff and mentioning a lot of stuff.
So you're looking for a shallow mount sub, correct?
http://www.edesignaudio.com/ed...d=106That's the only other one I know of besides the ones you mentioned.
Now, hard hitting and loudness depend on your enclosure, amp and amount of air your subs move. Also, why would you have 3 amps, yet only use one slim mount sub? You might as well just find a multi-channel amp (5 or 6 chan.) and use that. That will help free up space and save you money.
Anyway, you already have a nice sub (the typeX), why not use it in a custom enclosure to help alliviate wasted space?