Vintage Integrated Amplifiers With Great Sound

What vintage integrated amps from, say the 70's-80's-90's can be found at relative bargain prices, but provide really good sound quality? 

Not many, what is your budget and what loudspeakers are you driving. 

I could budget up to $3500 for something really nice. 

I still don't know what loudspeakers you are driving but let me throw this out there. A Musical Fidelity integrated. They will match well with most loudspeakers and have a classic appearance. I would try to find one that is less than 20 years old to avoid a lot of potential problems. There is a really affordable 3.2 on sale right here.