It's actually hard to buy an expensive used enlarger lens these days without trying...the prices on them have dropped probably faster and farther than any other piece of camera equipment. Which is, to me, great news.
I like Nikkor and Schneider enlarger lenses, and you can find good ones at or near your 80mm target. (I've also heard a lot of good about the Wollensak 90mm lens, but have no personal experience with it. I'm sure that other companies have made great lenses as well, but through happenstance I've ended up with sets of newer Nikkor and Schneider lenses, and they're all excellent performers.) Keep an eye on eBay; every now and then you'll find a number of the same lens listed to close within a day of each other. Given the dearth of buyers for these things, the prices will be held low by the temporary oversupply. Patience is worth more on eBay than any other skill. Avoid buying the first or last to close, and you should get a deal.
Best of luck to you.
Dave