I am hoping to gain a better understanding how the CPU and GPU interact with each other, mostly in terms of how one bottlenecks the other. I've posted in several different locations about which GPU to get for my rig and have gained a great deal of knowledge from several excellent posters. However, it is still unclear to me how far I should go in upgrading my card.
PSU isn't the only influencing factor, I have learned. Matching CPU to GPU is also important. How can one tell whether the graphics card he's looking at won't be overkill for his system's CPU? That matters, right?
There is no golden rule for matching a cpu/gpu, as which will bottleneck depends entirely on the game and resolution you play at.
On the same computer, same game, you could find your GPU holds you back at 1080p, while dropping the resolution to 720p relieves workload from your GPU and you'll than have a bottleneck at your CPU.
On the same system, using a 1080p monitor and playing 2 different games, you can change bottlenecks quickly. Some games like Skyrim and Starcraft 2 are very CPU heavy and not threaded well while also being easy on the visuals, can easily become CPU bottlenecked. Other games such as Crysis are very GPU demanding and will become GPU bottlenecked on the same system.
Your usually fine and won't have any major bottlenecking unless you do something absurd like pair a $60 Athlon II X2 with a $400+ GPU like the GTX 580. If your getting a high end GPU, get a high end CPU.