From what I know, you'll need a Scosche adapter for the antenna connector when you swap out headunits to non-Infinity based ones. On top of that, you want the pre-out to be 4 volts for any replacement HU in order for it to play nicely with the Infinity amp our cars use. Overall, what I would suggest you do first is swap out the stock door speakers for the Inifinity Reference 6032cf ones. It will make a world of different in sound quality, and give you even better bass/highs control overall.

At 50 bucks, it's one of the best bang-for-buck investment you can make for the little Crossfire. I myself kept the stock headunit, but put in the above mentioned Infinity speakers in the doors. I use my phone with a bluetooth FM transmitter from GoGroove for my music needs. Anything from Google music to Pandora and XM subscription. Works very well, and when people hear the sound quality from the bluetooth FM transmitter they always ask for the price and place they can buy it themselves.