I can't find any detailed info. on the motherboard. My Medion desktop PC originally had a 250 watt FSP PSU fitted.
It doesn't tell you whether the 4GB RAM is the maximum that can be installed, or whether the HDD is a 5400 or a 7200 RPM unit. You could contact PC World or Medion, and ask them about it. I would also ask whether or not swapping out the GPU will invalidate the warranty.