WolvesSoulZ 
Supposedly their SPX-pro series uses a vifa xt19 variant. It's only good on axis. I don't think I'd recommend much beyond that. I just got rid of an Alpine deck due to some response issues that weren't just in my vehicle, but VERY noticeable on a sound board as well. I'd like to point out that Pioneer has some very nice speakers and head units.
I'm a fan of a warm/laid back sound with nice detail. I can't say I've listened to any of their current line up but I'd probably refrain from upgrading the rear deck until last. Install is going to be most important. Even $5 speakers can sound phenomenal if install takes into account speaker strengths/weaknesses; ask the guy who designed orb speakers.
