I seriously doubt you will get the same performance from a med to high end GPU from a low to mid end CPU especially a dual core one, thats not saying that it wont work, but it will utilize 85% of that GPU and not its 100%
And regarding in-depth bottlenecking articles have been done with modern hardware :
please use this :
http://www.anandtech.com/show/6934/choosing-a-gaming-cpu-single-multigpu-at-1440p
and i quote in the conclusion :
A CPU for Single GPU Gaming: A8-5600K + Core Parking updates
"if I were gaming today on a single GPU, the A8-5600K (or non-K equivalent) would strike me as a price competitive choice for frame rates, as long as you are not a big Civilization V player and don’t mind the single threaded performance. The A8-5600K scores within a percentage point or two across the board in single GPU frame rates with both a HD7970 and a GTX580, as well as feels the same in the OS as an equivalent Intel CPU"
Now i dont want to start a debate on intel HT and AMD modules ... but i did extensive research and truly its way to long to write in this forum and i am not feeling like it but i concluded that AMD bulldozer/pilediver threads are equivalent of 4 logical cores (i compared an Trinity x740 with Old AMD quad athlons )however intel HT on the i3 series if compared to the pentuim and celeron dual core without HT, you will notice that i3 HT will give you UP to 22%-25% performance on multi-threaded work load, and with 10 increase in TDP, however its still a dual core with 25% boost
So for single GPU gaming to get the most of it you will need 4 logical cores/or threads, using the above research you idiots
and yes the Intel i3 can beat AMD quad cores, if the software taxes only 2 cores.