That's a small form motherboard, only has one PCI-E slot, so no you can't use 2 video cards working together. You can add a second video card, but that's only for more monitor support.
For your power supply and CPU, something like a Radeon 6670 or a 6770 will work well, as long as the power supply is a good brand. If it's a cheap one, stick with the 6670. Either of those cards is around a $100 give or take, and both will be quite a bit faster than your 9600gt.