@kep5niner A couple of suggestions:
1) Consider the back-up G5 inline with the bottom of the G3X
2) GSB-15 USB powerport with USB-C jack. The cheap cigar lighter adapters are electrically noisey and don't deliver the average.
3) Revisit the autopilot decision for a GFC-500. The performance is unreal. With the GTN-650Xi + the A/P give you the SmartGlide feature when engine out.
BTW, many do not realize the auto-trim feature is optional and skipping it saves almost $6K. I installed a full Garmin panel last year similar to years in a 182 without auto-trim. I've flown several long cross countries in all conditions. The system seldom asks for manual trim. Auto-trim can go in later, just ask the installer to leave pigtails in the harness for latter installation.