What used speaker would you buy with $20,000-$35,000 and why?

I'd say in most cases, especially ss amps and preamps that holds very true......speakers are all over the map, there's a 30K pair of Martens on GON for 12900......will they beat a pair of Mag 20's in most categories?  no.......so does that mean they're overpriced?  who's to say.......most would say new Maggies are severely underpriced........

So what do you get with Maggies that others can't touch:

There's a definite sense of space around instruments that create an eerie realness and it's primarily a function not only of speed, but also dipole dispersion that's close to perfect.....instruments on a stage create a lot of their image by reflecting off the back wall as well as directly and dynamic speakers with a few exceptions just don't reach that element.....

The downside has always been the low end, but the 20.7s pretty much negate even that argument if you feed them what they want, which is a lot of SS watts with high current, coupled with a great tube preamp......

I've owned 30K speakers......I now own 6K speakers......

Give them a chance if you can deal with their size......they're very forgiving in terms of placement.......some listeners even listen to them with the edge of the panel facing them.......LOL

I would try some Grado PS1000e headphones for a paltry $1,700 and see if they satisfy your musical needs. Amazing sound there, IMHO.

If we are going that route we should do LSD or shrooms...

I wouldn't recommend that, based on personal experience. The last time I tried that stuff, an orange rhino walked into my condo from the patio and started berating my modest Ax-7e/P3esr setup, and boasted on how his McIntosh system was SO MUCH BETTER...  :-)

In terms of the thread, if I'm spending my own money I would look at Harbeth 30.2 or Magnepan 3.7i, and bank the rest.

If I'm spending your money, I'd look at either Wilson Max-3 or Tannoy Westminster Royale SE.

FWIW, if it were my money, I would buy a used pair of Sonus Faber or B&W speakers. I'd buy as high in the line (used) as I could for my $20,000.
You won't regret it!

Here’s a pair of the Linkwitz LX521’s with the ASP and multichannel amp - ready to go. I almost bought them... but... already had the Orions and couldn’t justify the expenditure for another set of Linkwitz speakers. Not sure the guy has sold them yet - you might check with him.

They sound like Maggies... but... with better bass and dynamics.  Same soundstage and imaging, because they're open baffle, dipole speakers.  I have the Maggies also... and... I prefer the Orions for the reasons mentioned.  Very much the sound of the live music performance.

https://www.audiogon.com/listings/full-range-linkwitz-lx-521-2015-08-02-speakers-07930-chester-nj

They also sound a lot like the Grado PS-1000e headphones mentioned above - which is spectacular... but... with a more realistic soundstage.