I would definately use the AthlonMP's, I have a Tyan K7 Thunder 2462UNG with 2 x 1.2AthlonMP's, 1GB ECC REG PC2100 Crucial, Adaptec 3200S with 4 x Seagate Cheetah X15's in RAID 0 + 1. WEhen I first got my Tyan K7 Thuner, I wanted to see if regular 1333 TBirds would work in it, I triued it out, they do work, but it is very lacking in performance and the are just way too hot. The performance of 2 1333 Tbirds isn't much better then the performance of a single 1333 TBird, they just don't take full advantage of the 762NB and SMP. I did notice a huge differance when I installed my 2 x 1.2AthlonMP's, I would spend the few extra $ and get the MP CPU's, you will NOT be sorry. I would also get a very good HSF, the AthlonMP's still give off a good amount of heat. I am using SK-6 with Delta 38's on my 1.2 AthlonMP's and they still run at 45C according to the Tyan hardware monitor in the Bios. I havw 2 extra 1.2 AthlonMP's, I am just waitig for my second Tyan K7 Thunder to return from Tyan from being RMA'd, I have a Revision 1 board that was bad, couldn't get any video out of it no matter what I did.