THE ANSWER IS ......
Go to the CPU database on the home page of overclockers.com. Go look at the highest overclocks achieved. SEE the motherboards that have gotten the best overclocks most often.
That will tell you which brand to target. THEN, go pick a motherboard with the features you want, e.g. do you want onboard lan, firewire, etc. etc..
With unlimited funding, I usually recomend a motherboard with the fewest features. This way, if you LAN won't OC well, just replace it with a card that will. Integrated motherboards in general are great at saving cost, and usually OC well, but for the top OC, you're safer with seperate componets.
KT333 or KT400? Right now, the KT400 does not have a 1/6 divider, and probably won't, so KT333 or KT400 should OC just as well, of course the KT333 have been out longer so more folks know how to tweak the KT333s. ON the other hand, if you're pimping your stuff out, the KT400 has 8X AGP, (raedon 9700) while the KT333 do not.
SIDE NOTE with unlimited money AND time ..... there will probably be some (UNKOWN) ocing improvements in the next few months. The KT400A should have a /6 divider, and the Nforce2 will be able to lock the PCI and AGP independent of the FSB. Of course, there are no firm dates on either one yet, so know idea how long you will need to wait.
Good luck.