First off, I haven't installed any power adders to any of my rides but having friends who have, I have a little knowledge on this. Using some of the information you provided and a little help from the internet, your ride rolled off the assembly line with 210 hp at the crank and 240 ft-lbs of torque. That's what you have to look at, torque. HP is a byproduct of increasing torque. The model designation for your transmission is 5R55 which in itself contains some useful info: the first 5 is the number of forward gears, R is for the alignment of the transmission to the car in this case Rear, and 55 is short for 550 ft-lbs of torque. That's about what your tranny can handle give or take a few ft-lbs and depending on how you drive it. Now as far as the mileage you have, that's a significant amount to start adding boost. My family has driven many Fords and most of which have had their trannys overhauled at about 100k. (89 Taurus - 80k, 97 sable - 97k, 2000 E250 - 118k) My 98 GT was a manual which was overhauled at 160k and my sisters' 2000 Taurus is on borrowed time as she's approaching 150k with no overhaul...yet.
With all that info, there's nothing wrong with adding boost...just check out the health of your transmission first before you start investing thousands. My 2 cents would be to look at changing the differential gear, increasing the injector size, a tune, cold air intake and headers. This will help your car do better with what it already has. A good
suspension will help as well. Look at spring rates before you buy; the greater the rate the stiffer the ride. I had an
Eibach Pro-Kit with some Eibach Anti-Roll sways and Bilstein shocks and struts. Totally transformed the vehicle. My suggestion would be to look at progressive springs as linear springs tend to give more bounce and are not as comfortable. Your back will thank you later.
A 100hp shot of nitrous may be an option if you want to go that route. Larger shots are also available if desired but that wouldn't be for continual everyday performance. Turbos are also available but if you think that a supercharger is expensive...just wait. In addition, more (expensive) parts will have to be installed in addition to chassis stiffening, etc.
Being that your question was open-ended (not sure if that's what you intended), I hope that I have provided some insight. I will leave you with this: there is no replacement for displacement. If more everyday power is what you want, an engine swap (or car swap) may be the answer you are looking for.
