I'll definitely be overclocking but I'm not planning on trying to break speed records here. I'll be doing some gaming (LoL, Skyrim, BF3 on med to high perhaps?) but don't plan on doing SLI or Crossfire. I'll probably have a boot SSD and a single, large HDD for storage so this enormous "mid" tower ATX cases with 6 HDD slots just seem very pointless to me. I think I really only need 2 5.25" drive bays - one for a fan controller and one for a ODD (though I haven't ruled out going external). I want a rig that's pretty quiet but I'm just planning on doing aircooling so it doesn't need to be totally silent, nor does it need to be frosty cold. I also want a case with a small footprint as this will be used in a small bedroom (hence the need for quiet, as well).
So after typing this out, it definitely seems pretty obvious I should go mATX but I'm just wondering if there's anything I'll be missing out on if I switch to mATX (never built a mATX rig before) or if ATX would be a better form factor for getting a good balance of silence / cooling. Thanks for any help and for making it through my wall of text!