vintage versus modern speakers

If I recall correctly, Nelson did not design any SAE stuff. I believe that Jim Bonjiorno did that basic design on your amp, although I know that Ed Miller put his hands in several amps of that era also.
Since I've chimed in... My 2 cents on the speaker discussion.
Basic design parameters hasn't changed. There were some nice speakers put out in the late 70's & 80's... Jon Dalquist had a few, Infinity, DCM was ok, recently I have been modding an Altec A7, they have turned out quite nice. What has changed is, Material technology... we now have Kevlar, carbon fiber, magnesium, aluminum, ceramic, pulp wood fiber cones & yada yada yada... This has changed along with a much improved manufacturing process. We used to have measure 50 drivers to match up a half dozen to tight tolerances. Today, they come off the line within 5% or better tolerances... Combine that with better caps & resisters along with compensation circuitry not typically used back then and normally, Yes, today, overall speakers are better, but there is no doubt that there were satisfying speakers of yesteryear that if found in good shape could offer some enjoyment.

I don't disagree with all of the above, but I would add that The Doors LA Woman album for example is very listenable because in part at least it was not overmixed. Some of the old Chicago as well. I admit though my editions are remastered as well.

The vintage AR's, specificly 9's and little brothers, were not "hollow in the middle" but were set apart and easily distinguishable from competitors by their balance, midrange presence, flat frequency response and were not popular with the rockers. Point being that flat frequency response is not the only factor distinguishing vintage speakers from contemporary brands. The vintage AR's still don't hold up in comparison to today's audiophile brands. But if flat frequency response is the main consideration, get a pair of early 80's AR's. There are still plenty around.

I note that the OP indicated a budget of $1500. My suggestion is that he go to the Audiogon home page, click on "speakers" on the left side of the page, then click on "continue to all speakers listings" on the right side of the page, and then in the "narrow by price" boxes on the left side of the page enter a min price of $1000 and a max of $2000. That search presently returns 147 listings. I suggest looking through those listings, picking out several speakers that strike your fancy, and asking for comments on those specific models.

My guess is that the sweet spot in that price range for price vs. perfomance, together with minimal condition-related risk, will generally be speakers that were made between about 1990 and 2010.

Regards,
-- Al

On the question of best speakers for $1500, unfortunately that is not a lot to get into really good towers, and American made doesn't make it any easier.

With a big amp like the SAE, if the OP could stretch his budget to $2000, Ascend Acoustics is an American company that has been making excellent speakers for over a decade, based in California. Their Sierra Tower is right up there with Salk speakers(also American), but more affordable. I just bought their Sierra 2 bookshelf speaker and I am seriously impressed.

Raymonda nailed it when he said

generally one can spend less today and get much better sound per dollar than yesterday.

IMO, partly as a result of what Timlub said:

Material technology... we now have Kevlar, carbon fiber, magnesium, aluminum, ceramic, pulp wood fiber cones & yada yada yada... This has changed along with a much improved manufacturing process. We used to have measure 50 drivers to match up a half dozen to tight tolerances. Today, they come off the line within 5% or better tolerances... Combine that with better caps & resisters along with compensation circuitry not typically used back then

to which I would also add:
computer modeling which cuts R&D costs substantially, and
lower cost manufacturing sourced from third world countries.

At the other end of the cost spectrum are the high 5 to mid 6 figure speaker systems which would have been beyond anyone's wildest imaginations "back in the day".