However what will make it fun is that you have to justify your choice. Again ruled by your own guideposts, but for example you might ad in to your excellent post about Boston Acoustics vintage speakers how they compare to modern speakers, or perhaps their current lineup (different company I know, but still might be interesting). But pretty much what you and others have been posting so far works great, I've been googling up the examples right along, fine suggestions all.
My Audio memory would be stretched to think back to when those babies were new...
I did organise a pair of A70's (or was it A75's) for my brother when he was living in NY - that is over 10 years ago now - I think he still has them in storage somewhere.... (the joys of globetrotting)
Honestly, there are a lot of good speakers that have been made over the years, and most of the good speakers (even some of the great ones) get forgotten.... and rapidly lose value once that happens - so there are bargains to be had.
Another example - Klipsch Forte .... typical traditional old school Klipsch, Horn top end and mid, in this case with standard woofer and passive radiator (bass horns take a lot of room!)...
This is a take no prisoners grab the audience by the throat speaker - but only when driven with a gutsy yet refined amp - 100W minimum (?).
Also this speaker doesn't "wake" up until you give it some stick - play your music loud and it wakes up and sings.... try to play it quietly and it just gets dull....
Whereas the Quad electrostatics - my reference - will play very very quietly indeed without ever losing anything (ambient noise permitting obviously) - which of course allows them to reproduce fabulous micro detail from almost any recording. But they just won't move enough air to thump you in the gut with the bass. It's not that the bass is not there... it is! - especially with the newer 989 - but the earth won't move for you.
Which brings me to value speakers that are true references - Quad Electrostatics...
A vintage ESL57 will not play low down, or high up, but the midrange will make you cry. There is a reason why so many speaker designers have kept a pair of these around for reference....
Essential to have the right amp for them - with impedance dropping below 1ohm they NEED current - but if the voltage rises too high, they will arc and self destruct - so you have to have high current but relatively low voltage (low power).
Quite a few valve amps are a good match, some transistor amps too - these are absolutely legendary - and usually great value - just make sure that they have been looked after, or have a quad specialised tech to look them over.
It is easy to self destruct these with the wrong amp...
I've seen these sell for as low as $500 a pair
Going more recent - the ESL-63 was around for 20 years, and was almost identical to the current 988.
The 63 is much more robust, likes a more powerful amp (doesn't have to have one though), images brilliantly, again limited bass - due to limits of air movement - but the bass that is there is beautiful, detailed, accurate - a reference speaker.
Stereophile rated it class A with the proviso that it was not totally full range due to bass limitations (goes down to only 35Hz.... )
I tried a number of times to match a sub with a pair of these before giving up - no sub could match the sheer speed of the stats, and the end result always sounded wrong.... in the end I bought the later ESL-989 which has an additional pair of bass drivers.
You can usually pick up a pair of these for around $1000 (or a new 988 for about 5 or 6 times the price...) - again the smart thing is to have the panels checked - a wild listener with a powerful amp can cause damage to the panel.
Are these a little finicky - YES
Do they sound brilliant - YES
Positioning - they need a largish room - they like at least 3' / 1m behind them, but are not sensitive to side walls - so you can put them up against the side walls, but you need to provide air behind them.
My Quads left due to lack of space in my current premises .... replaced by a very nice pair of Gallo Nucleus Reference 3.1.
The Gallo's are also good value (the Ref 3.0 and 3.1/3.2 particularly - the current 3.5 is getting pricey) - they are a much newer speaker (reviews on 6Moons) - and side quite a bit like electrostatics - but with bass!
Ultimately they do not have the inner micro detail that the stats can expose... but this is only obvious on highly complex dense music - like symphony orchestras - where the Quads will seperate out the instruments quite clearly, and the Gallo's won't quite achieve it. Compared to the Quads the Gallo's are pretty much indestructible. And they can work well with a wide range of amps - the bass will work best given serious power though. (Anthony Gallo demos them with 500W amps) - should be able to find them under $2000.
Two other completely different speakers worth considering from among the classics, which are sometimes to be found at bargain prices: Klipsch original Klipschorn and LaScala.
Totally different sound to the above - and the Klipschorn requires a room with two corners into which to place them - the horn and the LaScala are true horns for tweeter midrange and woofer. The Horn puts out 114db/W (!!!) - so the key is not "lots" of power, but making sure the power that is delivered is really clean and low noise...
The LaScala's have been used a lot in night clubs - and can sometimes be grabbed used from these premises when they close down....
Again I've seen these speakers (pairs) for between $1000 and $2000.
Browse old (early/mid 80's) audio reviews - look for the very top of the line speakers from back then - and then go hunting for them...
They will mostly sell for under $1000 now, and will (if not hammered by a tyro owner) perform on a par with many of the top speakers of today.
Bye for now & Good luck in your search
David