what model is your power supply? a decent one would run a 750ti or lower. a real crap one might not. a 750ti would actually be more gpu than you need for non gaming uses so you could get an even lower powered card. there are some with as low as 30w tdp that would run a simple pc.
what specs do you have now? something newer would have a built in gpu that would be enough as is. something like an i3/i5 with the 4000 series integrated would be enough. an amd apu would be plenty as well if yu have that.