SiS chipsets are a bit underrated, mainly because they were cheap and generally used in low-end boards. Such as this one. The SiS630ET is pretty comparable to an Intel i810E, which is not bad if you're after an office box, but not great then or now if you want to do high end (period) gaming. In fact the 630ET beats the i810 hands down on a few counts, particularly relating to memory (both clock speed and max amount). But still no AGP.
If you want a fast Tualatin-supporting chipset with AGP, look for the SiS635T. It's arguably the fastest So370 chipset, supporting 1.5GB of DDR-SDRAM and AGP 2.0. But as it's a performance chipset from a vendor that manufacturers only used in the low-end, boards with it are very rare. ECS P6S5A is one example, Jetway had two uATX boards, and Asus had the CUS266 (at least on paper - never seen one in the wild) and that's about it.