The ST6 is a very good stable MB. You might have to do the wire trick to get more voltage for your 800Cel if you want to really push it. You most likely will have to do it when you put a Tually in though.
I had a [email protected]
in mine for a while but didn't really need the extra voltage. I found I got a few more fsb Mhz out of my ST6 compared with my P3V4X. I wouldn't expect much more of an overclock compared with your Soyo, but hey, its begging for a Tually!
Everything else is just normal trial and error with bios settings, updating to latest Bios, applying latest drivers...etc.
Some negatives for this board is the 512Meg memory limit, (same with all i815ep) and the onboard sound tends to crap out at high PCI speeds. (but not many people will use it anyways)
But its a good cheap upgrade to almost double your performance with the Tually added.