M-Audio's Key Rig (and a companion product, Drum & Bass Rig) was originally a software package, available for both PC and Mac. There was a favorable review of both products in the July 2005 issue of SoundOnSound magazine -- that's when and (mainly) why I bought them. You could use them as standalone synths or as plugins, and they had some nice sounds -- GM was covered, but only part of the package. I used them for a while, then Bandstand came along and (personal opinion) I thought it did a better job with most GM sounds. It looks like M-Audio now ships KeyRig only with a couple of its small controller keyboards, and only for PC. But you can still find the software package online here and there for about $70 (or apparently, $50 through at least one Guitar Center). And M-Audio's support page shows that drivers are available for Vista and for Mac through OS 10.5.2. Is it worth $50 - 70? Maybe. The review is still online at soundonsound.com, and I thought it was pretty accurate. It's a legacy product, but so is Bandstand, and while I was never bowled over by its GM sounds, it had some other synths and sounds that were fun to play with.