My God!, the Intel HD2000/HD2500 would probably outperform a 8400GS
Here we compare your card to the lowest card I recommend to any gamer, the fabulous NVIDIA "GeForce GTX650 Ti", not to be confused with the GTX650 (non-Ti).
- http://www.hwcompare.com/13937/geforce-8400-gs-512mb-vs-geforce-gtx-650-ti-2gb/
The GTX650 Ti is 10.21x times as powerful as your current GeForce 8400GS, worst case scenario.
- Where you're scrapping 6.25fps (terrible, more like a slide show if anything) a GTX650 Ti will get nearer to 64fps, if not much more.
The GTX650 Ti only uses 2.75x times the power to generate >= 10.21x the performance!
Heck, the oldest card I have is an ATI Radeon HD4890 and it's not in my main rig (obviously).