Gordon,
The guy I bought my Sequels from had a Mac Tubed preamp and Mac CD Player feeding signal to a Spectral amp driving them, and it sounded VERY smooth and clean. I'm not a big fan of Spectral's sound--it's a little too analytical for me, but tempered with the tubed Mac Pre, it sounded pretty sweet.
I've always like the look of Mcintosh amps, and with many speakers (especially high-efficiency horns) they can sound divine. But I've not really been "engaged" by the sound of Mac amps driving Martin Logans which I have heard in the past. Although they seem to be very clean, and have a lot of detail, there is just something about the Mac/ML combination that I find to be, well, just not very exciting.
Perhaps it's that the setups I've heard were the older, VERY inefficient MLs. The Gen3 Martin Logans have MUCH smoother-sounding panels and some have on-board dedicated amps for the woofers, so maybe they sound better with Mac Amps. But I haven't had the opportunity to hear a Vantage, Summit, or Spire driven by a Mac amp, so I can't say...
But I will tell you that the first amp I ever just completely fell in love with was a pair of Mcintosh MC-75 monoblocks I saw in a store in Wheeling WV (Blacks Stereo and Hi-Fi,which is, sadly, gone now) when I was in college. They had been completely restored and re-tubed with OEM tubes, and were driving a pair of Klipsch LaScala's with signal from a Studer RTR tape machine. I've always wanted a pair of those, but I've never seen a set in decent condition for a reasonable price since then. I think that was in 1986, and the owner of that store was asking $500 for the pair. I saw them about a week after I'd bought my Carver M-200t. I've always wondered how things would have turned out for me if I'd bought the Macs instead of the Carver that summer...