Oops, "Enter" posts it.

This website will give you a good sense of which parts can fit together: http://www.logicalincrements.com/

It also has a total price from each row based on parts. Might vary some based on where you buy.

Edit of Caution: Look at each piece and hypothetically put it together in your mind before you touch the pieces together. I tried to help a priest-age kid in my ward with putting his together and he had already smashed the CPU in. Two bent pins and a corner of the CPU tweaked before he even got to my house, and I didn't have tools to fix that or know if it's fixable.
Most things will fit together, but that's a bad spot to break.