Is my amp the problem?

Stringreen what Class D amps have you heard and what are you comparing them to?

thanks.

Have not heard that exact amp but have heard Crown Class D amps at the gym and I own other Class D amps.

One thing is all Class D amps have very high damping factor including that one and the ones I use. Good ones do bass in particular extremely well, better than most anything else. Hence their popularity for use in powered subwoofers. When I first heard mine, I thought bass was gone also in comparison but turned out to just be more dimensional, articulate and clean in stark comparison to prior which was more towards stereotypical "one note" fatter bass which many may be used to and may seem like more or better but is not IMHO.

Stringreen, I have been told the same by other people as well. I am too far down the road now. Maybe in the future I'll reconfigure. I  have been fine tuning it and it sounds pretty good right now. Still needs more impact but I have some options. 

almarg  2)The miniDSP 2x4 has a very low input impedance of 6K. 

I'm going through the same impedance woes, with yet to arrive a Minidsp 2 x 4 HD to do some bass (<150hz) only experiments with, it's 10kohm input, a little higher than the 2x4.
I sent a email off to tech dept of mini dsp to see if the analogue inputs are a fet based input, if so then "maybe" the 10kohm smd load resistors can be swapped out for >50kohm?
This should be an easy way out if the source has high output impedance.

Cheers George