Lots of good advice. Just a few things to add:
1. That guitar-mounted DPA mic might sound great... I dunno. But it's about the same price as a used KM184, and for sure if you were going to sell one of them in 5 years, you'll get pretty much your entire $700 back from a used Neumann, and less than half that for the used DPA. I agree with jimmyjazz that the Gefell SDC mics (M300 or M295) are at least as good as the KM184, but they're a lot less plentiful on the used market.
2. You could make a case that if you're also planning to record vocals with the same mic, perhaps you'd be better off with a large diaphragm condenser. If so, I agree with the 414 recommendation. My personal favorite for a secret-weapon LDC is the Blue Dragonfly Deluxe (has to be the green "deluxe" model and not the regular dragonfly... they only made 275 of them). I have owned several of them... they come up used for around $750, and they just murder everything else in that price range, IMO. Poor man's cardioid-only U67.
3. Stay away from the new LDC Neumanns (TLM series). They're straight trash. I'm shocked that such a venerable company puts a Neumann badge on them.
4. If you're not doing vocals, I like the idea of a used Neumann or Gefell, and put the rest in moveable acoustic treatment (wall panels or tubetraps) that will serve you well for both tracking and for mixing. You will get life-long use out of these things.