ALi's chipset could be good... my last system was also based on a P5-A, I ran a K6-2 350 @ 460mhz (115mhz * 4 @ 2.6v) rock solid for over a year!
The later P5-A bios versions fixed the AGP problems, (or maybe I was just lucky) coz my vidoe card was a Viper V770 32mb AGP Ultra (TNT2U).
anyway, the SIS chipset will probably be stable anough, just slow :|