I'd love to help scratch that building itch, but after reading a horror story or two, supporting business servers on your lonesome is a PITA. Not impossible, as you can buy duplicate parts for backup, use hardware RAID, etc, etc, but is it worth the time and headache when the goal is to minimize downtime? Heck, I'd think a buisness would quickly do away with you if they find you costing them inordinate amounts of time.
I have yet to build my first desktop, but even I know that Servers != Gaming PCs. Let the giants handle the server support, they have entire teams on tap for that stuff.