THe ST is a great car because of the amount of fun you can have for the money. If you load it up with every option imaginable it will come in less than a loaded WRX while giving you much more interior refinement, and technology. The only thing missing would be AWD and truthfully to most people that does not matter one bit.
Not sure I understand your post about the STI nearly as fast. It is faster, but a loaded STI costs 10k more than the ST, and your still stuck with a car that looks 10 years old on the inside. I have not seen a comparison between the MS3 and ST, but I would bet it would be super close in both a straight line and 'in da twisties'. Plus the Ford Looks 100% better on the inside and out side (in my humble opinion).
All your options sound like good ones. Good luck with whatever you choose.