Best Vintage Speakers?

It all depends on size requirement of the speakers that can fit your room and the amps you have to drive them.

Vintage high efficiency speakers from the late 50s and early 60s are extremely desirable.
12" ~ 15" Tannoy, Jensen, Lorenz, Altec, Western Electric, Coxials
Vintage JBL, Altec, Jensen, Klipsch horns
Rogers and KEF LS3/5A speakers

If you like midrange and imaging, and can forego high volumes and driving bass then it's hard to beat Spica Angelus. You can find them used for under $500 and I would wager that for chamber music they would be impossible to beat.

They are quite tricky to mate with a subwoofer (I tried) but they have very controlled bass so they can be used in very small rooms (if the aesthetics is not a problem).

A great bargain.

All Apogees.

Be very careful on selecting vintage ribbon speakers when they get old. Especially if they came from high humidity environment.

SANSUI SP-200 and SANSUI SP-2000 - BOTH are amazing alternatives to Advents and ARs. Maybe not the best but certainly excellent performers- huge sound, reliable and good bargains