After thinking about what all of you guys said, I decided to wait until the sale on NCIX(store in the area where I live, so no need to pay for shipping), and today they rolled out great savings.
Got my hands on the following for 89.99$! (almost the same as the used one but with warranty and no shady deals)
"Powercolor Radeon HD PCs 4850 625MHZ 512MB GDDR3 PCI-E VGA DVI-I HDMI Video Card "
http://ncix.com/products/index.php?sku=40867&vpn=AX4850%20512MD3%2DPH&manufacture=PowerColor&promoid=1097
This one is based on the chipset 4850 that Tom's recommends and checked it should run my only game - Starcraft 2 on Ultra settings!
Thank you again everyone!