I've been researching this very issue for the last 8 hours.
I like to make an informed and informative decision. =P
The VIA K8T800 chipset is the best choice for now. It beats the Nforce3 150 and 150 pro chipsets almost every time. The SiS 755 A2 chipset is currently only available from ECS and comes on a value board with limited features. The ECS Board has put up very good numbers in comparison to other boards but it maxxes out at 2Gb DDR, up to 400Mhz, with only 2 slots available. If you're looking for IDE raid onboard with more than 2 drives the ECS board isn't a bad choice though as it has room for 4 drives. I've almost decided on the ASUS K8V board. Just waiting to hear/see its Benchmarks stacked up against some more Mobo's with the same VIA K8T800 chipset.
Hope that helps. =D
AMD Athlon XP 2100+-=-1Gb PC2700-=-40Gb WDD HDD-=-
16x DvD-=-32x12x40 Lite on CD/RW-=-Floppy, "Who needs a damned floppy!"-=-ECS K7S5A Pro-=- Geforce 4 Ti 4400 128Mb 4x-=-