yes. But if possible, upgrade to 3570K and overclock, which will get you better performance increase. If not 3350p will do. your videocard is high performance enough to fully utilize a quad core intel.
depend, i5-3350P have slower clock. but more core. What are you using it for? better off with a i5-3550 or better
It's in a mini-itx case with no room for anything but a stock cooler. Also the SFX form factor power supply is limited to 450 watts. It doesn't come in any higher than that so I'm thinking overclocking is not an option.