Did you seriously bump after 9 minutes? Wow.
Anyway, I don't do the builds like others do, but I would recommend looking a the builds on the forums:http://www.tomshardware.com/forum/296090-31-best-configs-budget-intel-based-gaminghttp://www.tomshardware.com/forum/296094-31-best-configs-based-gaming
Those would at least be starting points. In terms of 32 vs. 64 bit OS, 32 limits you to 4GB of RAM for the system, including any ram on the GPU. 64 limits it to 128GB I think, so essentially there is no cap on the 64-bit system. As the minimum requirement for SC2 is only 2GB, technically you could get away with a 32-bit system, and not run into a problems. However, it would be advisable to go with 64-bit, just in terms of availability, and the ability to put in more if you want/need it.