Great old speakers that are as good as new ones

Altec model 19 or JBL over klipsch but keep in mind all old gear may need some upgrading or repairs. Also old loudspeakers make work great when you purchase but can fail.They are old after all. So if you can not repair or DIY. Might not be the best deal to buy vintage.

Quad 57 or 63's, Klipsch Heritage line, AR1's, Magnepan Tympani's.

Alon I,II,& IV

Energy 22 - it was too cheap for it's quality even in 1982 when it came out.

In general the ferro fluid can dry up on tweeters and both woofers and tweeters can be damaged from misuse so you buying really old bargains that are no longer supported does bring problems.

If you buy old used and abused ATC's then you are in luck as they continue to support all their products and a re-cone job can be done by anybody with an ounce of DIY skills.

I have owned many speaker systems. Some with a a price tag as high as $10,000. Picked up a pair of 20 year old Fuselier,s.
Best sounding speakers I have owned. I paid $500 for them at an estate sale.