yep you dont need the top end cpu's if all your doing is basic stuff. in fact you might be happier with a £350 laptop. it will do everything you want it to and can even be hooked up to your tv to watch a movie if needed.
personally i wouldnt bother with an fx4100 or anything like it instead an amd apu(cpu and gfx all on 1 chip) A6 or A8 build would likely be just as useful, cost less to run and wont take up to much space because you dont need to mount them in a big box case.
My socket says AM3+ so FX may work or may not, at least that is what i read here somewhere. My case is mid size for a ATX form if that means anything and so is my MOBO. I was leaning towards an APU, but don't know if it is compatible with my MOBO. I tried phoning ASUS and its frustrating they put me on hold and then eventually ask me to leave a voice mail so they can call me back...so i hung up.