|The EVGA boards are only marginally better at overclocking quads. The asus board will hit close to 400 FSB with a Q6600. The EVGA (new revision only) can go as high as 440 FSB.
I dont know where you get your info from, but the 680i's are not a better choice for a Q4. Frankly if you can get anywhere close to 400mhz on a 680i...you deserve a cookie. There are numerous users on this forum, that report the mobo being unstable at higher FSB's using a Q4 cpu, rather than a C2D. There are also, many different methods, for modd'ing the mobo to add stability for a Q4 OC.
i have to run now, but search on this forum for the 'P5NESLi-680i, help thread' in the mobo section. You can see Uslatin's postss regarding this topic, as well as MHill...both who own the 680i and a Q4, and are very dissapointed in the mobo's performance capabilities with the Q4.
As for the P5K, I have had no issues, going all the way up to 490mhz FSB, so far, using my Q4. I am currently running 430mhz FSB @ ~3ghz..sig verified. It is by far the best OC'ing mobo I have yet to lay hands on...even surpassing my P5B-DLX...a much more expensive mobo.