Any video card would be an improvement since you are currently using integrated video. What power supply do you have? The 6670 is a low power card, but it is still too much for say a 300 watt no name power supply. The label on the power supply should list amps available on the +12 volt rail. Something in the 17-18 range would suffice, but 20 or more would be better.
A definite yes on the ram.