my new computer help please

im going to buy a new computer from dell heres what im thinkin about. First of all I'm buying from the outlet and im restricting myself to computers that were ordered and not shipped out. heres the question Im thinking about dell deminsion 5150 which is better I play (multi-table with pokertracker) browse web, and was thinkin to getting into some gaming. Whats the differnce between the 3 and 3.2 processors and the 128 and 264 graphics card? and is this computer upgrade friendly? and other comments or critizims welcome thank you in advance