Bob,
There is a database of CS5 and CS5.5 performance benchmarks that you may want to look at.
I think you have your general answer already. But if you want to look at tuning your specific computer for Adobe Premier Pro performance, you can see the relative times to perform export and some other tasks here:
https://ppbm5.com/Test.html
Basically, end users are asked to run a standard CS5 or C5.5 project, with 4 different tasks, then report their results as a total time and 4 separate times.
You can search the database on specific components. I have a PC with an i7 920, so I searched on just that CPU, then looked at the graphic cards that people were using for best performance(GTX 460, etc.), how much RAM (I just went to 27GB, which is plenty), etc. It can help you compare your own equipment to determine your expected results.
There is also a good site with a discussion of those same benchmark times with various Nvidia cards, with different numbers of GPU’s (CUDA cores.)
There, the bottom line is: ANY Nvidia card – with 96 to 480 CUDA cores (GPU’s) – will speed up export by at least an order of magnitude over the software only Mercury Engine. The incremental benefits of going from a GTX 450 to a GTX 470 are smaller. (Sweet spot seems to be the older 460 at around $120-$160)
https://www.studio1productions.com/Articles/PremiereCS5.htm
There is also a hack there to turn on the hardware GPUs in any Nvidia card (only a few are completely tested and approved by Adobe, but almost all work.)
If you download a 30 day trial of Production Premium and run the tests it might all make a little more sense. Then you can mine that info to configure your system for best results. (I don’t know if you can still download and run CS 5.5, so CS6 might be a wild card, but it will tell you where you are overall in comparison.)
Good luck!
Best,
Michael