Upgrade video card or new desktop

my current desktop

P5qpl-am
e7500
4gb ddr2
9500gt
600watts psu
AOC 19" LCD

i can play old games but i wanted to play new titles in medium settings 1024X768 resolution. and im planning to buy a new card HD 6850 ($152)or build a new desktop:


CPU: Amd Phenom II x4 955 3.2ghz be
MOBO: am3+ Gigabyte GA-990FXA-D3
RAM: Gskill Ripjaws X 8gb 4gbx2 Ddr3 1333 CL9 0r 4gb 2gbx2 DDR3 1600

Total: $294 (14760 in phillipines peso) of course this is a hard earned money working $16 a day.

new card or new desktop?