g3x gtn avionic

I’m owner of a Piper Cherookee PA-28-151, 1975. It’s already equipped with a GTN 750 navigator and a piggyback GMA remote audio panel and intercom. I’m consider installing a G3X unit and a GFC 500 Autopilot. I will also replace the existing transponder by an ADS-B in/out unit. A G5 or GI 275 as...