I use the Mark Levinson No. 23 with the Studios. They work great and I recommend it highly. (I would stay away from the 27 and 27.5, not because it would sound bad, but just because it would not have the power the Studios really need. I used to have a No. 27, and upgraded to the 23 after a month or two. Just not quite enough dynamic headroom for my listening tastes.)
BTW, I would have gotten the ML 23.5, but did not have the money at the time to get that particular amp.
The ML 20 series amps should work ok. Since they are monoblocks you will get more current than the 27 series, although, they too are only rated at 100 wpc. My guess is that it would work fine, but that is a guess.
My opinion is that any really good, high quality, 150 wpc or more, amp should work well with the Studios. (You probably need to double that for the Salon, btw.) However, with tube amps, I would think 200 wpc would be the minimum, since the speakers have an impedance 4 ohms.
My two cents worth any. Good Luck in your search!