My Magneplanar 1.6QR's (just two-channel at this time) sound wonderful with the 990. What I especially enjoy, and didn't really expect, is the wonderfully clear, tuneful (i.e., pitch of instruments clearly distinguishable) low bass, which means 40Hz with the Maggies. The amplifiers the 990 drives in my system are nOrh Le Amp 2 monoblocks, so I can't comment on the contribution of the 7500 amp.