Buying 4gb of ram, dare I mix and match?

So im going for the almighty upgrade and gonna get 4gb of ram

I choose to get 4x DDR2 1gb, i have 2 questions

which is best

PC6400 667 or 800 mhz? This will be a gaming rig and not overclocked

also is it ok to mix and match ram, ie 2x1gb of corsair and 2x1gb of kingston?

thanks
mark

Not a good idea to mix and match. Id go for 800mhz just to try to get the ram as close to the CPU as possible since your not going to be ocing it.