I'd be interested to hear someone's comparison, too. I run TAD CR-1's, and recently acquired an M900u to try with them in place of the PS Audio BHK 300 mono's that I have been using. The stereo Luxman amp is bringing some clear virtues in the mids and highs in terms of revealing musical and harmonic information, and that is appealing; but I find that I am not as happy with its low-mid bass, where it seems less distinct, almost feeling a bit vague. This surprises me, given the 700+ damping factor that the Luxman boasts - - I would have expected greater control and definition, and I am hearing the opposite.
Yes, the stereo Luxman seem able to play loud enough in my 22.5' x 15' x 8' room. But the bass quality in the match to my speakers could be better, I'm feeling.
So, if going to mono blocks would improve this bass issue, then I would have to consider if I can go that far in budget! I hope someone has direct experience that can speak to this aspect.