Guys, at higher resolution CPU bottlenecks the GPU, not in lower resolution. I think you have misunderstood the behavior that in low resolution games can perform more better with the addition of a more powerful GPU. The reason is that at low resolution a standard card like GTX 460 or HD 6850 cannot overloaded with the calculation amount and more data CPU can provide them, more performance will be gained. But this is not bottlenecking.
However, in very high resolution, starting from Full HD, CPU simply cannot process data as fast as GPU can and here GPU is also overloaded with high amount of data. At this time you will feel the need of a more powerful CPU.
E4500 is a good processor and very good overclocker. With the stock cooleer you can easily reach 2.4-2.6 GHz. I know it as I've personal experience with my 2nd system in Kolkata. And it can handle the GPU like GTX 6790 @ 1440X900 resolution pretty well.