Hmmm, see if you can get a hold of a Voltaire ISR 9024D-M. They're probably the best 20Gb/s speed combination of capabilities & noise. Anything that's SDR is likely to be extremely noisy, so you'll want to avoid them.
That being said, I haven't used any of the Flextronics switches in person. So that one may be an exception. There's more info about IB switches suitable for home use here, if it helps:Suggestions for *quiet* Infiniband switch?