The computer is in a mid-ATX case (ATX). The power supply you linked is an ATX power supply.
Yes they are compatible!
I don't know the quality of Diablo PSUs. However, I know that Corsair PSUs are good and reliable.
I suggest this one: http://www.newegg.com/Product/Product.aspx?Item=N82E16817139027
($40 after MIR)
Thanks, I didn't that sounded right... The uatx crap or whatever....
I think i might get the corsair, because all i've heard was positive things about their products.