If you can get hold of one, you might like to get one of the new KT133a chipset boards. These allow a true fsb of 133MHz, and so overclock much better than the KT133, which won't allow a fsb much over 110MHz. Two excellent KT133 boards are the asus A7V and abit KT7-Raid, so if you could find them with the new KT133a chipset I'm sure they'd be great boards - I think they're called the A7V-133 and the KT7a-R.
A good heatsink would be the globalwin fop38, though the fan is extremely loud ;-) If you don't want the noise, the alpha PAL6035 is a good one to look out for, and the alpha PEP66 is probably the best - though you'll have to modify it (cut a couple of slits in the aluminium duct) to get it to fit. I don't know about the US prices, but I reckon you could get a great mobo and hsf for about $180, probably less, so you'll have plenty of money to spend on the cpu. If money really is no object, get a 1GHz tbird and oc it to 1100 or 1150, or even a 1.1 or 1.2gig tbird, though they probably won't oc very well (tbirds have a ceiling of about 1300, and that's with very good (ie water/peltier) cooling. If you do want to save some money though, a slower duron (750 or 800) would almost certainly get to a gig on aircooling alone.
PS just remembered, there may be some problems getting the PEP66 or FOP38 to fit on the abit board - I know the PAL6035 fits fine, but the area around the socket is quite crowded, and I don't think the PEP66 will fit (you need a really thin fan to fit it on the KT7-R). The FOP38 should, hopefully somebody that's tried it on the KT7 can post with an answer.
