Need Help with Vid Card and psu

ok this is what i have currently(keep in mind all parts in box still)

-Intel Core i5 760 Quad Core Processor Lynnfield LGA1156 2.8GHZ 8MB Cache Retail Box

- Arctic Cooling Freezer 7 Pro REV.2 CPU Heatsink Cooler LGA1366 LGA1156 LGA775 AM2 AM3 W/ 92MM Fan 1

- G.SKILL F3-12800CL9D-4GBRL Ripjaws PC3-12800 4GB 2X2GB DDR3-1600 CL9-9-9-24 Core i5 1.5V Memory Kit -50895

-Western Digital Caviar Black 1TB SATA3 6GB/S 7200RPM 64MB Cache 3.5IN Dual Proc Hard Drive OEM

-ASUS P7P55D-E LX LGA1156 P55 ATX DDR3 1PCI-E16 4PCI-E1 2PCI USB3.0 SATA 6GB Sound GBLAN Motherboard

-OCZ ModXStream Pro 600W ATX 20/24PIN SLI Ready Modular Cables 135mm Fan Active PFC Power Supply

-Coolermaster Haf 922 Mid Tower ATX Case Black 5X5.25 5X3.5INT Front Audio USB eSATA No PSU

-Samsung SH-S223C 22X DVD Writer SATA Black OEM

-Microsoft Windows 7 Home Premium Edition 64BIT DVD OEM

-Acer H243H BMID 24" LCD Monitor

- and possibly add my multi card reader from old pc

main purpose pc, gaming, playing poker bit surfing, watchinng movies

so my main question is....i have around $300 to pop for the vid card won't be going sli, so one card it is, i was thinking the msi 470gtx twin frozer or is an ati chipset one of equivalent better, example say a 6870 or 5850?......and is my power supply sufficient?, i bought the psu in a haste as was a doorcrasher thing and couldnt refuse the price, but after doing more research , little leary if i oc my processor and vid card and mem abit

thx in advance

Actually that 600W PSU is pretty good according to jonyguru.com. I'd get the 470 GTX personally. Even though it's not listed, I assume you got an i5-750/760?

I would say wait for the 69xx series to come out from amd in the next coming weeks. You already have a relatively capable gpu to suffice till then. Just my two cents