the thing is, for your budget your better off to build a whole new pc or order a custom built gaming rig if you want the software and warranty, depending on who you buy off of a warranty is a nice add on
if you decide to build your own, maybe you could check out the custom gaming pc sites to get an idea of whats out there and decide what you want
me? I prefer to build my own as I have done in the past, the only problems I ever had, I had gotten a brand spanking new bad memory stick and zipzoomfly.com replaced it no problem and I also had gotten a bad processor, in which newegg.com screwed me on when they charged me to repair it....cost me $60 to repair a brand new never used processor, they said thats the best they could do because I couldnt prove that it came that way....fuckers!
Learn the basics in this "how to" video for new usersHERE
Learn the basic console commandsHERE
Learn how to create keybindsHERE