i've found that the 2.4's usually do 270+ fsb (in my experience) ... newer 2.6's should be about the same (a little lower) but put less stress on the rest of the system ... the trick is using good memory (Adata PC4000 or OCZ PC4200) to get those speeds. The M0 chips require really good memory and motherboards to get the most out of, 300mhz fsb isn't out of the question.
the 2.8's i've used max out around 240-250mhz fsb (non M0 stepping) and give nice results with PC3700 or pc4000 memory that can handle those speeds
M0 chips are the good stuff I ordered a M0 2.8c from
http://www.azzo.com/af4/details.asp?ProdID=826
and should have it by monday
I'm hoping for 266-270mhz fsb out of it 3,780mhz wow (if I'm lucky) the rest of my system has seen 274+ fsb 1:1 so the memory/mobo and everything won't be holding me back
I guess any 2.4c or 2.6c will do honestly unless you're looking for some benchmark records