Many of the issues in the current G5's (and I suspect this goes for other PCI devices besides the UAD-1) are due to issues with the AMD-8131 PCI-X controller. The latest dual 1.8 G5 does NOT use the AMD-8131. So far, it is the only G5 model that doesn't use it. In preliminary testing, the dual 1.8 G5 performed much better than a dual 2.0 G5 in terms of how many plugins you can run, when using built-in audio. However, performance varied quite a bit when using other audio interfaces, and also varies depending on whether you're running multiple UAD-1's or not. We're looking into it.
Most likely this computer will work fine for you, and depending on your setup may work better than other G5's. If you have any issues you might want to try different settings for the AMD-8131 mode... A clean install on this machine should set that setting \"off\", since it will detect that there is no AMD-8131. However, this machine (as well as all other non-G5 Macs) will also work if you turn *on* 8131 mode. The downside is increased host load per plugin, but on the other hand the UAD-1 DSP load will actually go down in 8131 mode. Depending on your exact setup, you might get better performance in 8131 mode.
Also note that this model runs the PCI bus at 33 MHz, and there is only a single PCI bus for all 3 cards. Basically it's like the old single 1.6 G5, except minus the AMD-8131 (which the single 1.6 used).