any MB (with P67 and higher) will overclock the same (apart from BCLK OC)...
non K can be overclocked by 600MHz+ over the stock clock,
let's say the default clock of the non K CPU is 3.3GHz (i5 2500), with turbo on 3.4 for 4 cores, 3.7 for 1 core in use.
now intel will allow you to use turbo + 4x, so for 4 cores it will go to 3.8GHz, for one 4.1GHz
on top of that you can add some bclk OC, let's say 105MHz bclk, so now you go for 3.99GHz for 4 cores, and 4.3GHz for a single core in use...