It really depends on what you mean by vintage! 30 years ago 50 watts was easy but almost all of it solid state much of it garbage. 40-45 years ago was the quote "golden age." I have a suspicion this is what you want. 60 watts per channel was almost unheard of except for the aforementioned EL34 based Marantz 9 which is a major target for Asian knockoffs not to mention the legitimate Marantz * reissue by VAC. Virtually every thing else was based on two tubes per side EL-84s whether it be the 6BQ5 (same tube) the slightly more powerful 7591, or the most powerful the 7868, they all ran under 30 watts a channel in real life. You simply need to get the right high efficiency speakers to use them. I own 2 Sherwoods with 7591s and 7868s they were a lesser known brand. Most people like the Scott variants and the Fishers, they rarely go for more than $500 except the exceptionally clean rarer models. If you want a real Marantz in great shape (mono blocks), they will cost you more than a very good modern amp, 8- 10 thousand. The Harmon Kardons were never that sought after but I don't know why, you might want to listen to some. Be careful about people who refurbish the amps so extensively they are really not vintage amps anymore, they have been modernized so you lose the vintage sound, if you really want it. I can tell you it has its moments but is not particularily favored in light of what you can get today sonically. Experiment, get one that works well and get some same era speakers and you'll know what it sounds like. Its somewhat dark sounding rolled off not much low bass (that takes power) it can be very sweet in the mids.
If you mean vintage like 30 years ago get the Macs they will drive almost anything. Or if you want the late 70s second age of major audio buying especially the big reciever or integrated amp try the Sansui, Kenwood, Pioneeer, Marantz (Japan), a really good example of a mid line one will cost you only about $300. By about 1980 Japan started outsourcing already to the rest of Pacific rim and quality dropped dramatically. Don't be mad if you find the sound not to your liking. The big problem with these amps and recivers is finding any left over or scavanged circuitboards.The older stuff was frequently hard wired butnot always. Repairs get expensive or are just not possible I spent nearly 6 months trying to replace a circuit board in a top o the line Kenwood and gave up. Therefore I highly recommend if your going this route let someone else do the hard work of getting the item into shape without detroying it's character.-