He said he was looking for something higher end, to me that spells out spending over $100 on a GFX card. Anything over $100 is going to be more than powerful enough to max out nearly every game at 12x8.
Bottleneck should apply to the slowest component in the chain, it has nothing to do with what frame rates you're getting. People call hard drives bottlenecks all the time, yet they have nearly zero impact on frame rates once the game is loaded up. Hell I'd call a monitor a bottleneck if it had slow enough input lag or response time.
I know that the E8400 is a powerful CPU, I know that it is more than satisfactory. All I'm saying is two things. 1. The E8400 is not high end by todays standards, so if the OP wants a higher end GFX card, he is going to be spending more than he probably needs to. 2. At 12x8 any $100+ card is going to move the bottleneck over to the CPU regardless of what cpu is in the socket.
Raidur :
The reason we see the CPU mattering more at a low resolution is because the GPU bottleneck is lifted. That is good for comparing CPUs considering the GPU is usually the bottleneck when gaming. Any game/resolution that lifts the GPU bottleneck is going to be more than playable, especially if it was playable at a higher resolution.
Unless the components are 100% equal in speed, the bottleneck can never be lifted, only moved. An old Pentium D 3.73GHZ will probably run most games pretty well, save for the hardest games out there. Throw a 5870 in that system, and drop the resolution down to friggen 320x240, the bottleneck is obviously on the CPU. Raise up the resolution to 2560x1600 with 6 monitors in eyefinity, the bottleneck is surely going to be thrown back to the GPU. This is an extreme case but it gets the point across.