I think he is confusing motherboard ram with Vram.
The memory on the graphics card is not the same as the memory on your system, it is built into the graphics card so it doesn't matter if your motherboard supports DDR2 or DDR3.
GDDR5 is faster.
Are you taking into account rebates?HIS Radeon HD 6770
$99.99 after rebate
check if you have at least a 450w power supply first.