I plan on using the Garmin GPS 175, interfacing through the Dynon ARINC 429. there are many options that interface through that, Dynon lists the third party navigators and radios that are supported in their documentation, I don't have the comprehensive list, but its not small. The autopilot panel is optional (although highly recommended). the COM panel is required if you use the Dynon Com, but that is optional as well, a Garmin 650 can interface with the Dynon, but I don't think you get the fancy EFIS COM interactions that are native with the Dynon Radio.Besides a Garmin 650/750 GPS, can you use anything else from Garmin with the Dynon? Specifically the autopilot controller and com panel? I personally don't like the dynon designs, just an opinion im sure they work fantastic.