I just bought a pair of Mani-2's and have been experimenting with amps to drive them. I started with a single Conrad Johnson MF2100 (100 w/c @ 8 ohms, don't know the 4 ohm rating). They sounded really nice with the 100 w/c, but when I added a second MF2100 in biamp mode they really opened up. I also am trying them with B&K M200 Sonatas (bi-wired, not biamped) which are rated at 400 w/c @ 4 ohms. They sound much better than with a single MF2100, and a little better than biamp MF2100s. I don't know if this is because of the higher power/current of the B&K, or it's just a better combination.
I'm not at all familiar with the 9100 . . . but hope this gives you a baseline.
I'm not at all familiar with the 9100 . . . but hope this gives you a baseline.