I am indeed sorry for the slight.. err.. 'vagueness' of the original post
I'll elaborate a bit then, and as i am now intrigued a bit, i'll add a bit more too
OK, just motherboard to be taken into account, none of this blueprinting and phaze malarki, although watercooling is viable, but im assuming that watercooling isn't efficient enough to warrant modding the motherboard (except maybe the odd pencil mod

)
1st off, the e6300/6400 based c2d, what would be best for these (extreme fsb really)
2ndly, the e6600/6700 range, again, ideally extreme fsb at max multiplier (or close to max, eg, 450x8 on an e6600 is obviously better than 400x9...)
3rdly, quad cores, now i was under the impression that these didn't clock as well as the dualies, but by all means, prove me wrong
The budget is infinite (well, it isn't, but i would basically like every option to consider

)
Just fyi, i have a bfg 680i and an e6600 at the moment, and the 680i isn't the best board for clocking, although not bad. I have had the cpu in windows at 4050mhz, but it isn't stable at all, is rather toasty, and has way too much voltage going through it for me to be happy with.. (3.6 stable at 1.5v, i run it at 3.2 for temperature reasons... reasons being, it makes me feel happier)
I am basically just toying around with the idea of finding a very nice clocking chip and, well, clocking it
Cheers for the info so far guys!