I built a SiS chipset socket 478 system for a friend a few months back, used a P4 2.53 GHz CPU, he wanted a fast 9x system, I used the on-board graphics and sound(sis 305), it worked a treat with Windows ME, all the drivers were available from the ASUS website. It also had the advantage of having a 3.3 volt AGP port, so later he can add a 3DFX Voodoo3 card if needed. It runs all the usual suspects like quake, quake2, 3, Unreal, UT, sub culture etc perfect on the on board GPU tho.
For myself, I run two SiS motherboards:
First is a ECS P5SD-AS VER 1.0a, that has a 5591/5595. It has 1MB cache and currently is the fastest result for Cyrix MII/IBM 6x86 in your VGA Database(entry 401), the on-board SiS 6326 has it's own RAM on the board and is connected via the AGP socket. I've always found the 6326 a chip that punches well above it weight. It also performs very nicely with PCI video cards, I am currently using a PCI Matrox Mystique 220 to complement the creative DXR2 DVD decoder card.
Secondly I have a ACER V75M, this one has a SiS 530 chipset, this board is from a IBM Aptiva system, it has a AMD K6-450MHz(currently entry 414 in your database), it's crazy fast for DOOM(as referenced here:"Super 7" SiS 530 chipset.), but most other things are happier on a external video card rather than the this time memory sharing 6326. My board has 512K cache.
I have just had come in today a PCCHIPS M590 that also uses SiS chipset, it came with a K6-III 400 MHz installed but according to all the internet info the board only runs a 90MHz FSB and thats debatable, so I will see how well it copes, I expect to put a Cyrix MII 333 in place instead at either 75MHz or 83 MHz FSB.
286 20MHz,1MB RAM,Trident 8900B 1MB, Conner CFA-170A.SB 1350B
386SX 33MHz,ULSI 387,4MB Ram,OAK OTI077 1MB. Seagate ST1144A, MS WSS audio
Amstrad PC 9486i, DX/2 66, 16 MB RAM, Cirrus SVGA,Win 95,SB 16
Cyrix MII 333,128MB,SiS 6326 H0 rev,ESS 1869,Win ME