I don't know much about IFR flying and will begin training after the aircraft is finished its upgrade. So I'm building it the way I think it might be most useful. The avionics will be as such: Stack PSA 450b Audio Panel IFD540 NAV/COM/GPS GNC255A or SL30 or Matrix1 NAV/COM (all w/GS) KN64 DME Transponder/ADS-B TBD PFD/MFD Plans are to go with the Dynon 10" and the D10A for a backup (when my plane gets added to the AML), and one other NAV capable display, possibly a G5. I think it might be nice to have the second NAV/COM for redundancy and for monitoring any GPS approach if ILS is also available on the same runway and for finding radials and intersections (the old way) if flying VORs. But yea, I know, the Avidyne will do all that for me based on GPS and/or its NAV receiver. Should I go with COM only for the second radio, or would a second NAV/COM be worthwhile? I can afford the weight and space, and can freshen up the KN64 with a new faceplate cheaply, but don't really know if DME is still useful. Keep it or delete it?