Yesterday I benchmarked with Aquamark 3. This is what I got.
Before:
- AMD XP2500+
- Asus A7N8X Deluxe
- 1 GB RAM DDR 333 dual channel configuration
- Aopen GeForce FX-5900XT
Score: 30500 points
Now:
- AMD64 3200+ 939
- Asus A8N Sli Deluxe
- 512 MB RAM DDR 400 single channel configuration
- MSI GeForce 6600 GT with 128 MB GDDR3
Score: 50300 points
Thats quite an improvement!

I've tested all my games at 1280x1024 with details set at high and I get excellent fps (2xAA, 4xAF): DooM 3, FarCry, HalfLife 2... I'm am very happy with the upgrade, it has been a seamless transition from AMD XP to AMD64. Everything is working perfectly

. One of the things that need special mention is PCIe: No more PCI (and AGP) lantecy issues, bandwidth problems, etc!
So if anyone is considering the upgrade, IMO it's worth every cent. I now have room for improvement in months to come: more RAM that can run in dual channel, faster processors, another video card to run in SLI, Windows XP 64 bits... New options are available