I am running straight pipes on my 99 GT and I like the sound, although I left my cats on. So, the exhaust passes through my cats first then through the pipes, which muffles the sound a little and also stops a lot of the back firing. I have run straight pipes on my 02 4.0L Ranger and on my 95 Lightning, I personally love the sound. Also, as with the power, look at it this way: Mufflers supply restriction, straight pipes do not give restriction. Look at the top fuel dragsters that run straight pipes right off of their headers....apparently it must increase horsepower somewhat or I don't think they would do it. Just remember to not just stop the pipe right after your cats, let the pipes go all the way to the back of your car or no less then the front tires or you could end up damaging valves. Also the shorter the pipe the louder it's going to be, more travel in pipe makes it a LITTLE quieter. That is just my experience and my .02 cents. Good luck and I am sure whatever you choose will sound good.
Oh yeah, best way to find out if you like the sound of straight pipes.....lift your car and take off the 4 bolts right infront of your mufflers and push the pipes apart and then start your car....that's pretty much how it is going, besides it will probably be a hair quieter.