1. I would recommend you to get a brand power supply (enermax, tagan, seasonic, corsair) 2. Your case is enough for a HD5850 3. No. (You should buy a better CPU cooler if you are going to OC) 4. Don't worry too much about that. A HD5850 is a decent card. Also, good decision that you buy an ATI card Could you send us the link from the shop?