I would think that the speakers and room acoustics would make a much bigger difference in regard to your ringing than the amplifier. You want to be able to tolerate a volume loud enough to mask the tinnitus but not so loud as to further damage your hearing. Certain frequencies will mask the ringing others will make it worse. If you can borrow a scientific tone generator you can exactly profile your own tinnitus then you could use a digital equalizer to cut back the frequencies that bother and advance those that mask.
Having said all that I think the Benchmark AHB2 would be a great amp for you. If one is not enough power then you can add a second down the line. Good Luck,
Mike