I work on a dual 2,5 Ghz G5 and it works great, make sure to have lots of RAM (i have 1,5 GB) thanks to the dual processor, the image renders about 40% faster because of the 2 scanlines. I think both processor aswell as RAM help to decrease rendertimes. The G5 is capable to have 8 GB of RAM, I think it's a good investment, however, the G5 2,5 GHz has a long delivery time, so instead you couuld choose the 2,0 GHz, maybe a little bit slower, but you can hardly tell i think.