I've been running testing on the G4s in Austin. They seem to be holding up quite well. The biggest issue is still hard drive. I added a Raptor drive to mine and it helped quite a bit. That setup got it as close as I could to the G5 model. I would like to say I could get you more results but that won't be possible since I have no more G4s to test with.

My biggest response to you would be to add a good secondary drive to the system. Keep the operating system and Catalyst/PixelMad software on the current drive and use the secondary drive for content only. That setup has sped up the performance here. It the same basic setup I've been looking at for months. It works very well. You will just have to get a good second drive. It needs to be at least a 10K rpm drive. Most below that just don't have the performance.

Hope this helps.

db