I haven't read your whole wall of text yet, but Twilight Princess was affected by two other merges shortly before the TFN merge which has made it a lot slower. I wouldn't use it for any kind of benchmark.
As someone who tests a lot of games, A GTX 460 (I have a 470 that can run pretty much anything at 3x) will run just about anything at 2X IR and not be GPU limited, and a 5850 I can guarantee will run most games at 2X IR.
2x IR is near HD, and most games will run at 3x IR on modern GPUs. If you want pure 4x IR for any game (except the aforementioned issues with Twilight Princess) a GTX 760 will do the job in pretty much any game. There are other limitations though that raising the internal resolution causes, like EFB2Ram strain on the GPU thread (which uses your processor, not your GPU). So, yeah, it's not really a good judge as to whether your GPU is getting maxed out anyway
As someone who tests a lot of games, A GTX 460 (I have a 470 that can run pretty much anything at 3x) will run just about anything at 2X IR and not be GPU limited, and a 5850 I can guarantee will run most games at 2X IR.
2x IR is near HD, and most games will run at 3x IR on modern GPUs. If you want pure 4x IR for any game (except the aforementioned issues with Twilight Princess) a GTX 760 will do the job in pretty much any game. There are other limitations though that raising the internal resolution causes, like EFB2Ram strain on the GPU thread (which uses your processor, not your GPU). So, yeah, it's not really a good judge as to whether your GPU is getting maxed out anyway