best used speaker for around 2500?

Depends on the sixe of the room. Reference 3a's would sound great in a medium to small room and maybe newform researches in a larger room. Personal tastes rule in the area of speaker choice. have fun listening.

Cbird

If you want an excellent full-range speaker, the Vandersteen 3A Signatures can be acquired for around $2500 on the used market. Even at MSRP, Vandy 3A and 3A Sig's are an excellent value, but at used prices there are very few speakers that compare. I have a pair of Vandy 3A Sig's, and listen to the same kind of music you do (plus blues), and prefer them to any speaker I have owned over the past 30+ years. Vandy speakers also mate very well with tube power amps, although your Copeland will probably have to operate in pentode mode if you listen at higher volume levels.

I do also listen to blues. room is 14 X 15