Vintage loudspeakers....Sleeper models....

Well, not sure what qualifies as vintage but I had a pair of Mirage M7si speakers (made almost 20 years ago), also a pair of M5si prior to that. Some consider the Mirage 'M' series speakers their best effort. These speakers were very well made - quality drivers - X over, good design, and NOT fancy cabinets. Plus the speaker surrounds do NOT rot like Infinity ... other models. They reproduce most types of music well and sound very musical. However they require decent amplifier power. I actually first used an older NAD 7155 receiver and then went to tube amps. I sold my mint pair of M7si's for just $150 a pair to someone local. Sad to see them go as they served me so well. That's a lot of speaker for the money. They are large so shipping is not really an option. You'd need some luck finding a pair local to you.
Good luck

OHM E, L, C2, H, I, Walsh 2,4,5.

I found a pair of EPI 100's in excellent condition and original boxes for $60.00.

Klipsch KG-4s. Not the best speaker ever made, but certainly a very good speaker for the money ($150 or less). Even better if you upgrade the crossovers.

critespeakers.com. Scroll down to KG-4

If the Sony speakers that you found are the ones I'm thinking of - they had a complex cabinet shape (vaguely Avalon-esque) - then they were much more than simply decent performers. I once owned a pair: nicely finished, wide bandwidth, and quite neutral, if not terribly dynamic. Great for jazz and small scale classical music, but maybe not the right choice for Mahler or Mountain.

Good Luck

Marty