This is just my opinion as I have no real basis to make this determination, but I don't think the power of your PC makes a whole heck of a lot of difference in how well or how difficult the AI plays.
There is a switch in the game options to use max CPU as well as if you're customizing opponents there are a couple of switches one of which relates to CPU utilzation, but while these settings may indeed make for a more difficult opponent I don't think it will make any difference from one computer to another.
An AI may play a bit quicker on a higher perfroming PC as opposed to a lower perfroming one but I don't believe that the AI will be any "smarter" just because a PC is faster.