Been there, done that. I would recommend that you research the watches that fit into your budget first. After that, try to pick an exact watch you're looking for. Let's take the 1680 as an example: for 5k the red dials are definitely out, but even considering the white dials, which Mk white dial are you interested in? What serial range? bracelet/head combo? insert, crown/tube, crystal, service history, provenance?
If the answers to the previous questions didn't immediately pop into your head, you'll need to do lots more research.
Good luck with your search!
JJ