$500-$600 gaming rig?

APPROXIMATE PURCHASE DATE: Within the next month

BUDGET RANGE: 500-600 after updates

SYSTEM USAGE FROM MOST TO LEAST IMPORTANT: gaming/general use

PARTS NOT REQUIRED: keyboard, mouse, speakers, moniter, OS

PREFERRED WEBSITE(S) FOR PARTS: newegg

COUNTRY OF ORIGIN: USA

PARTS PREFERENCES: none

OVERCLOCKING: No / Maybe

SLI OR CROSSFIRE: Maybe

MONITOR RESOLUTION: 1920x1080
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I want a PC that I can comfortably play RPG's like Oblivion, Dragon Age and The Witcher on. This is my first time building, and I'm excited to take up the project. I've been browsing the web, and this is what I'm currently looking at:

CPU - AMD Athlon II X4 620 Propus 2.6GHz 4 x 512KB L2 Cache Socket AM3 95W Quad-Core Processor

mobo - GIGABYTE GA-EP45T-UD3LR LGA 775 Intel P45 ATX Intel Motherboard

case - COOLER MASTER RC-692-KKN3 CM690 II Basic Black Steel ATX Mid Tower Computer Case

GPU - GIGABYTE GV-R577SO-1GD Radeon HD 5770 1GB 128-bit GDDR5 PCI Express 2.1 x16 HDCP Ready CrossFireX Support Video Card

PSU - OCZ Fatal1ty OCZ550FTY 550W ATX12V v2.2 / EPS12V SLI Ready 80 PLUS Certified Modular Active PFC Power Supply

HDD - SAMSUNG Spinpoint F3 HD103SJ 1TB 7200 RPM 32MB Cache SATA 3.0Gb/s 3.5" Internal Hard Drive -Bare Drive

odd - LG Black 22X DVD+R 8X DVD+RW 16X DVD+R DL 22X DVD-R 6X DVD-RW 5X DVD-RAM 12X DVD-ROM 48X CD-R 32X CD-RW 48X CD-ROM SATA 22X DVD Burner

ram - G.SKILL 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Dual Channel Kit Desktop Memory Model F3

Total cost after rebates: $575.92

I don't need something for online competitive play, but as I said above, I'd like it to run RPG's nicely if possible. Playing on maxed out settings isn't a necessity, but I'd like games to at least look good. Currently trying to play Oblivion on my MacBook Pro just isn't cutting it.