Lets start a bottle necking topic, for all questions about bottle necking to keep them all in one place.
A good rule of thumb that I formulated about bottlenecking between CPUs and GPUs is you want to stay in the same generation of each other. Also high-end with high-end for performance. A AMD A8-3800 will cause a GTX 670 to bottle neck, but not a GTX 550 ti. I hope that helps somewhat with understanding bottlenecking. FOr the generations it's a FX and FM2 CPU with a HD7000 serise GPU. A gen3 i5 and i7 with a GTX 600 series. This is for best performance.
utter bollox. you go off the cpus bandwidth, through put and threading perfomance. as well as memory and data trasfer speeds.
i had an amd am1 motherboard runing an athlon x2 4600+ paired with an 8800gt results were about 8% bottleneck.
i removed the x2 4600 and replaced it with a amd 6000+ x2 same generation arcitecture and the cpu had zero % bottleneck.
please dont try to blag round here because some people actually know there apples.
currently i run a 920 i7 D0 stepping thats 2 generations old... your gonna tell me it will bottleneck an gtx 680 or hd 7970 hahahaha.
chances are that 920 i7 wont bottleneck till gtx 880 and beyond.
I have a pretty bad bottleneck with my gtx 670 and fx-4100 even though I overclocked it to 4.2 ghz.
no doubt. because it has very poor single and dual threaded peformance thats comparable to the athlon x2 6000 which i already pointed to, had enough bandwidth to cope with an 8800gt but choked bandly with a gtx 270. so times the single threaded perfomance of the 6000x2 by 2 and you have roughly the overall perfomance of the fx 4100 which to all intents and purposes is the celeron of the fx range. the biggest card i would pair a fx 4100 with is the nvidia 650 or hd 7770 to build a balance rig.
for your system i would recomend an upgrade to the 6300 with a serious oc or 8350 but stay clear of the 8150. that should then balance out well with a 670. sell the 4100 on ebay or gumtree and get some money back for it.