Good luck mounting the cards (assuming you can actually get the 5830's). That riser cable is going to be a tight fit if you mount the cards normally. The power supply though, 650W is cutting it close. I'm sure it's high quality, but 5830's are going to draw close to 200W each if you overclock them (worth it).  I'd go with at least 750W or more with this. As I have found out, a dying power supply will take your motherboard with it. and sometimes other parts too.