Currently, the only USB controllers that we support are the Cypress SL811HS and the Phillips ISP1161A1. I don't think we have any immediate plans to support any other USB controller chips.
Off the top of my head, I think you would be hard pressed to get 20MB/s throughput but I haven't done any research and my hardware background is a little spotty. Heck, I think I'd be hardpressed to sustain 20MB/s throughput on my 1GHz Athlon desktop right now.
If you'd like benchmarks for the ISP1161A1 performed, I think you'll need to put in an official request to our support e-mail account
support@microtronix.com I hope this information helped.