U can never tell mate...
its the luck of the draw+ 4.5ghz stable is gonna be a bit difficult i would say...
my 2.8M0 was running @ 3.9Ghz 24/7 with 1.7V iddle so arround 1.62V load...
its a good chip that i havent sold yet that did 4328mhz.
i have now got my board modded so vcore wont drop

so i may just try again with it.
so i would say under 4ghz with your 2.8M0 and 1.75V might be possible.
a 3.4ghz northwood would be my no1 choise at the mo but i dont think spending £300 for a chip that would give me lower mem bandwith is worth it due to the the hi multi it has got.
the 3.0SL6WU and some SL6WK ones are supposed to have the same cores so we shall see what they can do once i get my mach 2 GT
so yeah keep that cpu and see what it does first before spenfing some extra money...