Didn't say SATA wasn't worth it. Hard disk access is amazing now. Just isn't the number one requirement when gaming. I didn't upgrade it for games.
Don't know why you are bothering with the MB and CPU upgrades though. Will make it a little bit better, but nothing truly amazing in games. A fair bit less money would get you a decent X800 or 6800, and either of those should cause some amazing improvements. Friend of mine has a 9800Pro with a 3Ghz P4 and he gets about 16000 in 3DMark2001. I've seen benchmarks online for the same spec PC with an X800 or 6800 getting near 30k out of the box. Some of them upto 32k. Upgrading that CPU to the same sort of speed increase you are talking about will be like upgrading his to a 3.6Ghz P4. And I'm telling you his benchmarks (with an upgrade of the 3.6Ghz CPU) will *not* get anywhere near the 3Ghz PC with one of the better graphics cards (GPU). Maybe get a couple of thousand more (say 180000, or even 20000 if lucky, and overclocked), but nothing like the GPU upgrade.
Going from a AMD 2600 to a AMD64 3000 is hardly a major upgrade for games anyhow. And def. not worth the money and hassle to do this.
ie. these days the CPU is *not* where it is at. It's the GPU (Graphics). And apart from some GPUs being too powerful for certain CPUs, then with a 2600 you will be fine for a X800Pro or 6800GT.
You were joking about the AGP remark wern't you? Won't even go into PCI Express then....
Cheers
Ps. Neofish : The MB is the £83 part of the list.
I am 99% probably lying in bed right now... so don't blame me for crappy typing