I'm shopping for a tuner at the moment, but I have to admit I'm lost. This is the first car I've decided to upgrade beyond air-chargers and exhaust (performance-wise), so I have no idea how these tuners work, or what the best one is.

Feel free to recommend your favorite tuner, please also say WHY it's your favorite.
My mods are listed in the sig.

 

more common - the biggest names in tuning use it.