So far Via has been by far the most successful chipset for the A64, but nVidia just came out with their nForce 250 chipset that I would go for if I was building a machine right now. (Stay away from the nForce 150)
There are lots of board reviews out there to look over before you select a particular board. Gigabyte makes good boards, but so do Abit and Asus. Check the recent reviews when you get ready to build to find the best performer...
Scout
700 Mflops in SETI!