I have had the GP6-400 (that's with a Pentium II400 inside it) for about a year and a half, and I must say it has been brilliant. Given my previous experience of PCs and Macs, which seemed to be forever crashing, seizing up, and generally being obnoxious, this little monster has been a very smooth ride. I am a computer musician, and running real time music applications, especially several of them in parallel, is about the most processor-intensive task you can think of; even worse than 3D accelerated games. Yet there has never been so much as a glitch. I can run three soundcards, a sequencer, Rebirth, the studio environment for my Pulsar card - all at once. Installation of PCI cards is really easy, and I have never yet had any conflicts. The only problem I ever had was installing a second hard-drive (musicians need tonnes of memory for those Wav files). This involved lifting out the entire cradle which contains the hard drives, and rather a lot of brute force was required to put it back. If you're not going to install a second hard drive, though, this is a great machine.