It really depends on what you want to do. The ideal kick size for studio use is 22" since it is very easy to mic up and record. Personally I love the sound of a 26" (Ian Paice, John Bonham etc) but they can be a bit of a handful if you get a novice or lazy engineer who might even (God forbid) ask you to take the front head off! Often I split the difference and go for a 24", but the best studio sound I have achieved (I think) is with a Gretsch 22" kick. Nice and fat and with lots of attack.
As for snares, the deeper the drum the higher you can tune it. 6 or 6 1/2" is great for studio use though. Ludwig 'Black Beauty' snares record wonderfully. I have a Ludwig Supraphonic and it does sound fabulous recorded. Bell Brass snares are quite harsh sounding, Steel snares are very bright and 'cracky', and wooden snares tend to sound warmer and fatter. If you are going the whole 'new metal' route though you might want to try a Piccolo snare, usually 12 or 13" and around 2 or 3" deep. Listen to System of a Down for a perfect example of this sound sound.
Check out some beautiful snare drums
here.
Hope this helps!