Well, the Asus has had a BIOS update that boosted its video RAM to 512MB - much better.
The Abit on the other hand.... I found a beta BIOS for it yesterday & loaded it up. S3 still no go (with no PCIe cards installed), but I'm told it might be due to my KVM.

Need to do some more testing today, but a couple of other problems I had seem to have vanished.
Justin