Thinking about Buying Starcraft 2. Need some help with PC

[SpartenOmega117]

so should i get a graphics card at best buy? Also I have an Hp a6110n. I checked the power supply and it said the max output was 250w. Anyways what do you guys think of the XFX- ATI Raedon HD4650 ($90) and the Nvidia Geforce GT240($110).