New help choosing new computer.

[Backwardsman97]

Well I've been looking for a new computer for some mild to moderate gaming. Nothing top of the line. I was gonna build one myself but I figured I'd just buy one already built since I don't want to do any serious gaming. Anyway, I just want a computer that can run the source games like CSS, Portal, TF2, etc. which are pretty old. It would be nice to run other games as well. I would like to spend right at $600 or less. Here's four that I wanted to decide between. All iBuypower but I'm not buying directly from iBuypower.

#1 - iBUYPOWER Gamer Power 538D3 Athlon II X2 240(2.8GHz) 4GB DDR3 500GB NVIDIA GeForce GT 240 Windows 7 Home Premium 64-bit - $569.99

#2 - iBUYPOWER Gamer Power 951i Intel Core i3 540(3.06GHz) 4GB DDR3 1TB ATI Radeon HD 5450 Windows 7 Home Premium 64-bit - $589.99

#3 - iBUYPOWER Gamer Power 540D3 Athlon II X2 250(3.0GHz) 4GB DDR3 500GB ATI Radeon HD 5450 Windows 7 Home Premium 64-bit - $539.99

#4 - iBUYPOWER Gamer Power 554D3 Athlon II X4 640(3.0GHz) 4GB DDR3 1TB ATI Radeon HD 5570 Windows 7 Home Premium 64-bit - $609.00