SPX Fitness uses the pilates reformer as a base and they do pilates type and gym exercises on it.I totally dislike it,has nothing to do with the integrity of pilates, but this is my opinion of course
I took a SPX class today at a studio in Palo Alto, Ca. SPX is a fusion of Pilates, cardio, and strength training done on a machine called a "Megaformer" which looks like a juiced up reformer. I thought it was a good workout:)
I have tried it and personally I don't enjoy it nearly as much as more traditional Pilates. The class I took really didn't have much in common with any Pilates class I've taken... seems like more of an amalgam of various exercises and has more of the tempo of a high-energy cardio class (including the music). I will say this, it was challenging.