New
#21
ATX is just a standard,
ATX - Wikipedia, the free encyclopedia
doesn't take into consideration what may be inside the unit.
As for a choice between the two, the GT 240 no contest. For the most part the GT 240 is about on par with the 9600 GT, with the major difference being the GT 240 is a Dx 10.1 card whereas the 9600 GT is DX 10. If nothing lese even nvidia makes the decision a little easier,I really want to fit the 240gt on it but i dont want to do something disasterously stupid. If the 9500gt is the safest way to go then i guess i'll have to stick with it.
GeForce GT 240
GeForce 9500 GT: a graphics card perfect for the ultimate 3D user experience and playing the latest PC games.
If you look at the specs they claim the GT 240 only requires a 300W PSU, with the 9500 GT needing a 350W minimum. As long as your 400W isn't of the quality like those in the article I linked too earlier, you should be fine with the GT 240.