Both are OK motherboards. I have the MSI KT4VL, onboard sound and lan, $85. I also have the epox 8k9a. The epox OCs way better than the the MSI. Epox, 200 FSB easily, MSI, about 170 FSB. Epox has no lan or sound, $85.
NOTE, the MSI KT400 currently DO NOT give access to the lower multipliers with the higher speed tbredB chips. The epox, abit, asus DO, don't know about the soyo.
IMHO, the cheaper boards with fewer "on board" stuff are better mobos for high end game systems. E.g. most on board sound uses the CPU for some processing, where a dedicated dolby digital card will do its own decoding, freeing up the proc. Also, dedicated sound cards are <usually> better than on board sound.
I'm also big on the KT400's right now, (A) cause they unlock the high speed tbredb's and (B) they have 8X agp. If your video card is not 8x AGP, and you have a sub 2200+, then a cheap KT333 would also be a good choice (e.g. abit KX7-333).
Good luck.