Decent enough system, has the CPU grunt required for what your doing. Plenty of RAM as well.
Gaming ability not so much, a GT640 isnt that powerful, but neither is TF2 intensive. Suspect as long as you don't start playing games above Counterstrike, TF2, Left 4 Dead level graphics you'l be good. If you do want to play higher tier games, youl either have to lower the settings a fair way or get a stronger card (and probably PSU to support it).