I've wondered about them myself, after reading this. I don't like Flowmasters (too loud) but like the cheap Turbos, problem with them is I can't get much use out of one before they blow their guts out.
I've heard Spintechs, and they sound sweet. This is the only video I could find at the moment. It's probably not going to sound like this on a Bronco, but it gives you an idea. They are 3" Pro Streets (1 chamber Flows equivilant) with an X pipe on a blown 306 Mustang. http://home.comcast.net/~cjshull/CJStangRun.mov