I have a Dual 1.4 G-4 with 2 180 GB in the vertical bay towards the back, an SATA card with 2 500's in the horizontal bay in the front. I was a bit concerned about heat and did have the CPU in a confined area but luckily I never experienced a melt down or heat issue. Since then I have graduated to a dual 2.0 G-5 and to be honest I think the former machine was faster. Just my 2¢ Frank PS G-4 is for sale if anyone is interested please email me off list fsudore at mac.com