VIntage Mark Levinson-ML3 verses no 20's

I am in need of some high current type amps that have a lot of amperage, like Levinson's gear but as well my hard to drive speakers need amps then can drop down to 2ohms! Can anyone tell me what the main differences are between say the ML3's and the 20's,apart from the obvious that 1 is a stereo amp, was thinking ML 2's but could use more of the wattage. As well buying amps that old are the parts available to service them etc
There is more that's obvious besides one being stereo and the other mono. The No. 20's are class A amplifiers and the ML 3 is AB. Mark Levinson amplifiers are known for a warm sound and the ML 3 is even warmer yet. The class A No. 20 has a clarity and transparency not found in the ML 3. Service may be difficult for either amplifier if you want it restored to exact original sonics and specs. Both are best if used with the matching Mark Levinson preamp and there is always the issue of camacs.
Thanks for the response, I have read the stereophile review of the 20's and was thinking 20 from the start, but I was offered a mint ML3 and just wondered if it would fit the bill,sorry for the late replay but I was unable to get back to this forum, the overall cost of restoring one or at least getting any of the Levinson gear up to spec is a bit scary to say the least .
I have recently joined Audiogon but have been into gear since my father purchased a Fisher 800b receiver in 1962. I have had Tympani 1Ds with the 3B bass panel, triamped using AR D100bs on the mid and tweet with a Threshold 400 on the bass panel, AR EC4 EXOver and Linn Table. Should of had the Velodyne 12 that I use now with my Levinson ML3, AR SPA8, Linn Table and Acoustat 2+2s - it sounds IMO phenomenal. The ML3 has the power to push any speakers that I have ever had. But if you want or need an amp stable to 2 OHMs then you might want to look at an ADA Select Series PF 201(Audio Design Associates, White Plains, NY)although primarily desigined for a whole house systems this amp is capable of powering 32 speakers with incredible stability well below 2 OHMS (it is in the .0xx realm) I used this amp to power a set of stacked Dahlquist DQ10s (4 - 2 0ver 2 with a Self Powered Velodyne 12) and it is still my Florida room system and it still sounds great. Also if anyone needs vintage or new Levinson equipment serviced get in touch and I will find the address of a factory authourized repair facility south of Boston, MA that took great care of my ML3 and was priced very fairly. Just cannot put my fingers on it tonight. However depending on your speaker choice your ears will dictate everything else that should go into your system - there is no right system for everyone - but there is the right system for me! And by the way I am listening to the Acoustats as I write this trying a new preamp that I have heard good things about - it is a Emotiva USP-1 that I saw was on sale so I ordered one. IT IS NOT GOING BACK!!! Albums played so far and so good- Thelma Houston and Pressure Cooker / Shelield Direct to Disc, ALan Parsons I Robot /MFSL, Al Stewart Year of the Cat / MFSL, Eagles Hotel California /MFSL and I have just turned over to record 2 side 2 of Pink Floyds Pulse Import on heavy vinyl on my Sony 707ESD CD player I listened to Steely Dan Can't But A Thrill. All sounded amazing and the USP-1 actually made me believe for the most part that I was listening to analog as it seemed to smooth out the digitalness (to coin a word I've heard often) of the CD. I am going to explore Jazz and Classical tomorrow.