Best Speakers with a DNA-1?

@cheeg "I’m sure it’s true that Vandersteen keeps improving their line, but have they changed them enough to make them better than the Vandys in the used market?" The answer to your question above depends upon when the used speaker was manufactured. The older the speakers, the fewer design improvements they will have.

"For the price of a new pair of 2Cs, I can probably pick up a pair of Treos in very good shape; where is the price break point?" The Treos have not been in the Vandy line for a long time so if you can get a pair of used Treos in good shape at anywhere near the price of new model 2CE Signatures ($2700) go for it.

Cheeg, go see Randy at Optical Enchantment.  He's over near the 3rd Street Promenade I believe:  http://www.optimalenchantment.com
He has a lot of great gear and has been doing this for years and years.  I'm sure he'd love to help you.  I don't know him, but friends who have purchased from him over the years love him.  They say he is not high pressure at all and loves to teach.  

Let us know how that goes. I don't know his full product line as I just did a search in your area.  I just got back from Pasadena for the Rose Bowl.  I used to spend a week or two a month in the 90's for business.  There was a great high end store off Colorado that had Avalon's.  Closed now, but in the day they were awesome.  

Oh, used Treo's are going for about 4,800-5,700 or so and they are rarely on the market. Right now there haven't been any on the market since October 2017.

+1 ctsooner, 
I bought yours.
I'd say that the prices you quote would be for the CT model, and those are as rare as hen's teeth.

If earlier comments are true, the old 2Cs are ‘magical’ — how much more magical can they get?

As has been said before, Mr. V. just keeps adding newer bits and pieces to his speakers, so the closer you come to current production, the closer you are to buying new. The differences are slight, but noticeable.
B

Actually there are none for sale right now.  The prices are for the regular and not the CT.  The only CT I saw that has sold went for around 6k