Want to build a custom pc

How powerful a PC are you planning to build? And is it a slim cabinet?

As powerful as I can and its not a slim cabnet

You arent going to want to use a GX 280, its going to be pretty tight fit and being a dell it likely wont take many standard parts. If its the mini tower the cooling is pretty poor, just spend an additional 50 and buy a good case that you will be able to reuse in the future.

I agree with Hunter.
A case is a excellent investment, and it looks to me that the gx280 is more of a office computer case, and like Hunter said, the cooling would be horrible.
I have a Coolermaster Cm690, its wonderful. Lots of vents, and even has holes in the back for liquid cooling, you could probably find one for around $50

Thanks guys,I'm gonna look into cases then