Levinson: 20.6 or 33H?

I have owned both. 33H is the easy pick (sound wise).

The Levinson 20.6 is an older design and in our opinion would not be a good choice with either speaker you mentioned. The 33'S would fit in with the Wilson's, but would not be recommended for the Avatar. Is that the correct Avalon model?
The Avalon Eidolon or the Opus would normally be the choice w/ the amps your considering. The Levison 33H amp is a fine amplifier but it's tonal balance would not be our first choice with these speakers. A high speed ultra-linear design would make the most of the quite different but interesting speakers.

Well, I'll post a contrasting opinion here. My bias is that I own the 20.6, and have only heard the 33H (a number of times, and the 33 once).

In my opinion, all the amps that levinson made after the 20.6 are bland and boring sounding. They *tried* to get a more 'tubey' sound and they just ended up making the amps sound dull, too laid back and uninvolving.

Other factoids: the 20.6 is a pure class A design and so uses 500 watts per each monoblock when just sitting idle. This generates a lot of heat and costs about $25 - $50/month in electric bills if you have them on 24 hours/day. As I understand it, the 33H are not pure class A, (and therefore have potentially inferior sound quality), but this permits them to have a stand-by mode which can save you some $ in electric bills.

Of course, if you are getting them for free, the 33H goes used for $14K and the 20.6 for $~6K, and the choice is clear :-)

I own Avalons and previously owned Wilson 5.1's. I've heard the 20.6's on the 5.1's, tho not on the 6.0's, and IMO the dark-sounding 20.6's are wrong for both of your speaker choices.
The 33H's are a reasonable mate for the 6.0, be sure to hear before committing.
With Avalons, many amps work well but ML would be well down on my list. Why not start with the speaker, then find the right amp?