Typically Diamond has had some great sounding amps. I've owned a pair of the D7's (monster 4 ch and mono) and have a d6300.4 now. When I used to sell them they typically were my go to amp for better systems.
Ill be selling my 4 channel later on this month to raise some capital if you're interested. it's a bit smaller in power output (37.5 w/channel) but sounds great. Very flexible xovers too.