Go for the newest Revision.
Thanks for your reply. Normally, I would agree with you, but Gigabyte still makes all three versions, 4.1, 5.0, and 6.0. It's not like the next version replaced the earlier one. But still I'm concerned that there might be a problem with rev 5, in particular the sound, because all the specs in rev 6 seem to be the same as rev 5, except for the sound chip:
http://www.gigabyte.com/products/comparison/list.aspx?ck=2&pids=5195,4602,4305
Originally, rev 4.1 had a Realtek sound chip. But that was changed to VIA in rev 5 (along with a change in theUSB chip), but they went back to Realtek in rev 6. So I'm thinking maybe there was a problem with the sound in rev 5 that was fixed in rev 6 by changing to the Realtek chip.