That Mb only supports 1x16 and 1x4 PCI-E slots.
@ Tombombadil9: How's the Old Forest doing, and do you still have those nice yellow boots, mate? (Hobbit in joke
You do n't give us your screen resolution, so I'll assume 1080 rez.
Something around he GTX670/HD7970 will do very nicely, along with a improved cooler for the CPU as upgrades-the i5 750 is still a very capable device and howls ou to be overclocked.
As always, check that the powersupply can handle the new hardware, for powerful cards its usually best to use dedicated PCI-E plugs rather tha molex/PCI-E adaptors.
BTW, I'm running a i5 750@ 3.4GHz on a Hyper 212+ paired wth a stock clocked HD7950@ 1080,it can struggle with the very highest setting on the most demanding games-Sigh.