I've no direct experience with SoloPro, but they have some very good instructors - Pat Washburn here, for starters. I suspect the school is very good.
Also consider evoschool.com - I've got much more experience with them (bias: I instruct for them). The Evo school has been around a while, their curriculum is very well thought out.
That said, SoloPro kinda HAS to be good - their instructor list is very impressive, lots of very talented drivers, and those that I know personally are ALSO going to be good instructors, from a personality standpoint - not everyone can articulate *how* to go fast, even if they clearly know how to do it. I've heard a lot of good things about SoloPro. I don't think you could go wrong with either one.