I've used the MS setups, they work well. They also sell an adapter board youll have to build into the empty case of an eeciv to connect to your stock wiring.... I'm gonna be doing this with a ms3 soon.
My my white car in the sig is using Holley HP... What a dream. Took me a week of nights to install (removed stock wiring) and get the random stuff to work right, such as headlights and running lights on the passenger side. The HP is awesome tho... I had my car tuned to the max with the A9L, ran good and put down 550 or so.... And I thought it ran good. The Holley ran better and was 80% tuned within about 20 min of startup after I figured out how to run the program..... And I didn't have a base tune to speak of. My car seems to make more power now, but the dyno says it's about the same.
Ive tried just about every standalone up to this point, either tuning friends cars or my own. Holley is hands down my favorite... It'll do anything.
The only standalone I haven't tried is that pro M stuff, but at $2k it's hard to do an experiment like that... Where I know Holley and where to go to get info and parts.