Nathan, you first must determine whether you want to take photographs or be an equipment junky.
I understand both aspects.
If your primary interest is in photography, the SLR and Rangefinder (RF) both have limitations and strengths.
If you use long lenses, close up work and are not concerned about noise/mirror slap, then stick with your Fm2N, I come from a Nikon F background and now use a Fm3A with motor along with an Fm2 that I have for long lenses.
But i do a lot of work up close with people and that's the domain of the RF camera. I started with M3 but coming from an F background with FTN finder, the lack of internal metering led to an M6 and then two M7's with Motor M's which are the ultimate expression of RF analog photography.
Problem being, the M series of cameras and lenses is very expensive new and used is crap shoot.
If your used to TTL metering, you may not be happy with an M3.
If you find that your Fm2N can't do something that a RF can do better, than find an RF camera to try but if your Fm2N does everything you require, why an additional camera unless you just want another camera.-Dick