Just remember when you're overclocking pre- i processor you're going to be overclocking everything your processor, and your RAM and I believe your graphics cards as well.
No, the Core2Duo and Core2Quad have separate frequency settings. I do run my E6400 "linked" @400MHz for 3.2GHz though, but the RAM is capable (OCZ Reaper HPC DDR2 PC2-6400). I forgot what I have my Q9400 running at (400MHz fsb probably), but it's options are similar. The E6400 is cooled by a Xigmatek 1283 and the Q9400 by a Noctua NH-D14.