As long as I can keep the M1 functional, I plan to do just what you suggest. If it becomes uneconomical to repair or replace it with used, then I may think about your KLN90 suggestion, because I like 3-4K better than 10 - 11K (I forgot about the pressurized antennae costs). I want to have two area navigators in the plane, (3 actually counting my IFR approved KNS80, my Loran is IFR enroute approved as well) as I fly direct almost everywhere, VFR and IFR (it's nice to live in the west). If I am going to replace the M1, something with GPS approach capability would be nice, and used KLN90s are low priced, I guess because of small map and usability. I care not about the map, and I'm a software engineer, so it will probably seem completely intuitive to me
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I did learn a lesson my previous handheld GPS. I had (still have) a Trimble Flightmate, one of the original aviation GPS handhelds. It developed a display problem, so I spent $300 bucks to repair it, thinking I was saving money over the $1500 for a 295. Three months later, it would not navigate any more, and estimated repair costs were $500. Time to quit, but it sure felt like that $300 was wasted... I don't want to repeat that experience with Northstar, as much as I like their unit.
Kevin