I'm not buying anything until I've been able to scope out what it has now for a CDI, antennas, audio etc. We're still working out the ferry flight details for now. This is all thinking out loud for the next 6-8 months.
Right now the only Nav it has is an ICS Plus Nav/Com with a display integrated CDI/GS. It's usefulness is debatable at the moment. That's it. The panel CDI/GS was connected to the dead KX145, so both of them do nothing now. I have no idea what this thing has for antennas, audio systems, room on the stack, etc. So nothing is set in stone until I can investigate further.
What I do know is that a single Nav with no DME and/or second Nav for cross radial isn't practical for IFR training (and is only partially practical for VFR use). We want a real Nav/GS with DME, which the KNS80 provides in one box. Like I said, the RNAV is a plus, not a requirement. I would have no problem with a Nav/Com and a separate G/S receiver, but that would cost 4x as much as one KNS80 and do less. I would also have no problem with an IFR GPS, but that is more $$ for features we don't need, and would lack a G/S.