Buying a new $700-$800(AUD) gaming PC

APPROXIMATE PURCHASE DATE: this weekend BUDGET RANGE: 700-800AUD (preferably max. of $750)

SYSTEM USAGE FROM MOST TO LEAST IMPORTANT: Gaming and general use

PARTS NOT REQUIRED: Keyboard, mouse, monitor, speakers/headphones

PREFERRED WEBSITE(S) FOR PARTS: umart.com.au, msy.com.au

PARTS PREFERENCES: I've pieced together some parts for the PC:

CPU: AMD AM3 Phenom II x2 550 $145
Motherboard: ?
RAM: 4GB DDR2 1066 (kingston HyperX) $99
HDD: Western Digital SATA 500G $73.50
GPU: ATI HD4770 HIS $155
Case & PSU: Antec NSK4480B-II with earthwatts 380 PSU $137
Optical Drive: Pioneer DVR-217BK $42
All prices in AUD

OVERCLOCKING: No SLI OR CROSSFIRE: No

MONITOR RESOLUTION: 1280x1024, but maybe as high as 1680x1050

ADDITIONAL COMMENTS: Thanks guys