I would personally reccomend the ABIT, because it has been a very good overclocker for my Durons. Why do you want to get a duron 600, and O/C it to 800? You can buy the ABIT KT7 RAID for $100 shipped, and you can get a 700 duron that will EASILY O/C to over 1ghz for $45. That would be only $145, leaving you $105 extra! You could pick up a 256mb stick of PC150 CAS2 for that, and still have $5 pocket change to get another fan!
Message me if you want some details of where to look and stuff.
By the way - I have a duron 700 for sale