I still have to hear any of the most covetable top-line vintage receivers in fully-restored condition. I'm tempted to track down a high-powered receiver (like Skylab's SX-1950) just for powering the HE-6 through the phone jack, even though it already gets more juice than it needs (and drinks it up happily) from the speaker taps of the receivers I've already got.
With my current setup -- high-quality vintage amps, near-TOTL recent-model DAC being fed data from lossless audio files (using
BitPerfect to improve the data output from my computer), I suspect I'm wringing all I can out of what I've got, and I'm tempted to stare down the rabbit hole of audiophile tweaks I'm currently skeptical about, like cables and power conditioners .
(Please let's not discuss that here. I'll ask a moderator to intervene if the conversation goes in that direction. Even if I agree with your post. Just... don't. If something interesting comes of my curiosity, I'll post elsewhere. If you have to get it off your chest, PM me instead.)
So far, the best receivers I have heard still fall short of modern high-end gear in the scale of the soundstaging, in the detail of quiet or complex passages, and the impact of sudden dynamic changes. In the best of circumstances, this gap in performance is small - vintage kit, even at collectors' prices, provides incredible value - but when you've reached the point where cost is no obstacle, you will still have to ante up.