The miniDSP is there for two reasons: 1) to match the room and sub, and 2) to provide a high pass filter slightly below the tuning frequency of the horn (and I also run a low pass at 200Hz just in case -- even though my AVR has a low pass at 120Hz). Number 2 is the most important as you don't want accidentally smash the moving parts of the woofer into the non-moving parts of the woofer.
Some amps have DSP built in. I bought Crown amps, which have a DSP but not one that will provide a high pass in the region where I need it. The XLS Crown amps are inexpensive. I bought my first at retail but my second off eBay (an XLS1500 to drive my Klipsch RF-7iis). Decent prices can be found on eBay.
I'm only using 1 of 4 outputs on my miniDSP. I'm running my 1 crown XLS1000 in bridged mode with 700w going to one LilWrecker wired for 8 ohms.
I could easily add a 2nd LilWrecker in parallel providing a 4 ohm load to the Crown which can source 1100w at 4ohms (or 550w per LilWrecker). And that would really rattle the house. If I wanted to break the foundation of my house I could add another Crown XLS1000 amp, use another output off my miniDSP, and drive two more LilWreckers. At that point I probably wouldn't be able to even hear my wife divorcing me.