I think people are going to steer you away from the FX-4100. Something like a i5-3570k is going to be a lot more reliable and better for gaming. A sata 3 (6 gb/s) hard drive would help speed up everything also, especially if you arent going to be getting an SSD to boot from.
I'd definitely stay away from the FX series as a whole for gaming. I agree with bdizzle, i5 3570k is the processor you want for gaming (anything higher is overkill). I might also recommend getting two GTX 670's in SLI to replace the 7970's. They're a mite bit cheaper than the 7970's, and give essentially the same performance. Apart from that, not much else to be said. You'll have to get a different motherboard for the i5, for which I'd recommend the z77 series of motherboards. SSDs are very nice, they cut load times way down (say when you're loading a map in a game, or booting Windows) but actual performance, as in fps or more eyecandy, is not where you would look for improvements in gaming from them.
the fx is a quad cpu dual module cpu basically it will perform like a dualcore with hyperthreading so will not have enough grunt to get the best from that gfx card.
they really are garbage.
if you want amd then get a phenom 2 955 or better. the 960 being the best buy for prerfomance to money spent. especially if your motherboard allows you to unlock it.
but if you dont already have the amd board then consider intel. get a much better cpu like the 2500k or 3820k roughly about that perfomance. and get a cheaper gfx card for now...
nvidia are only 4 or so months away frokm changing the game with there 7 series card. and so far theres no sign that amd will have anything near them, the 7970 is a great card but it wont do bf3 on ultra only the 670 and 680 will get near ultra @1080p or more.
spend a little more on the cpu and get a weaker gfx card for now. then when nvidia bring the big guns out get 1 of them...
bf3 on ultra in multiplayer is much more demanding than single player. the 670 benches at 55-80 minimum depending on howmany players and which map.
could be that much. its listed as q3 but may be the start of q4 due to low yields. also i think the 660ti is gonna be femi based not kepler. so no huge performance boost.
basically a re-branded gtx 570.(rumor)
if you can afford a 670 then get it. if not then the 570 or the 560ti... thing is if you can afford the 570 then theres no real reason not to get a 670 as it doesnt cost a whole lot more and will give half as much performance again.
saying that if you can afford the 570 but are pushing the budget then the 7970 is a batter option it should cost about $50/£30 less and give comparable performance. in some games it will be slightly better in others slightly worse. but not $50 worse.
I'd strongly urge you to listen to HEXiT as he's made some sound suggestions. You should try for the following in priority:
1. GTX670-OC'd (Gigabyte, Asus, MSI....any of them would be awesome! My personal pick would be the Asus DCII TOP)
2. GTX670- Non-OC'd (Gigabyte, Asus, MSI....any of them)
3. 7970 GHZ Edition - 'IF' you can get your hands on one!!
4. GTX670 - Reference
5. 7970 Non-GHZ Edition
Any of the above from 1-5 should manage BF3 on ultra with at least 50 fps@1080.
give your absolute max budget and how much you really want to spend. like you could stretch to $1200 but would prefer to spend under $1000.
any less than $800 and your gonna make compromises on components more than 1200 you can have all the bells and whistles.
http://www.newegg.com/Product/Product.aspx?Item=N82E168... ssd $205
comes to $1494 with 6 bux left over for some thermal paste if you want it.
i didnt pick any specific bargains or cash back deals (if there is any its unintentional). so choosing different parts may save you a few bux here or there and save some p'n'p
you aint gonna get much better... you could swap out the bd/dvd for a dvd ram writer and add the rest to the case of your choice but thats how i would spend the 1500