Recently bought a 1978 Cessna 182Q and looking into avionics upgrades. My airplane has basic six pack with GTN 750/GMA 350/GTX 345. Initially I was planning to go with all Garmin, GI 275 for both AI and DG, another GI 275 for the engine monitor, and a GFC 500 for autopilot. I got a quote of 51k...