High Sensitivity Speakers

I would not be in such a hurry to do away with them. Recap those old crossovers as I assume they have capacitors on there. Those degrade over time and I have had many 20+ year old speakers which have shown real improvement after recapping. Make sure all drivers are still well sealed to the cabinet. Might not hurt to do an ohm test and frequency sweep test on your drivers. If it is a sealed cabinet tap around the outside and see if your joints are working loose. Glue bonds do break and can cause ugly things to happen when volume is turned up.

I happen to prefer efficient speakers that are never less than 96db and the less the cone has to move to get your preferred sound level the less distortion you will have. Many older speakers are also made of plywood and not MDF and are far more durable. I have bought older speakers from people who did not bother to fix what they had and after getting them back right they were really nice.
  If you insist on getting something different I would suggest Klipsch. It is easy to get 101db+ very efficient speakers  that will last a long time and always have repair parts and good resale value. I don't know what your space is or your money to spend or how hung up on appearance you might be but you could go listen to a set of Jubilees and find out what less than 10g will really buy new. Old Chorus speakers are great picks but you will need to at least recap the crossovers but these will run under $1200 IF you can find some. I really really don't like MDF but I have heard the new Cornwall 4's and they are very nice.

" My recommendation, also to address the possible coherency issues pointed out above, would be to go all-horn from an arena in sound reproduction not commonly thought of as "hifi doable," namely Danley Sound Labs Synergy horns paired with Danley’s tapped horn subs. On top of the coherency offered by an all-horn approach you’ll have phase-coherent main speakers to boot - a "killer" combination, if you ask me. Think of models like SH50, SM96 or SM60F Synergy horn main speakers paired with two TH50 tapped horn subs. Any of these 3 main speaker models in conjunction with named subs would be a set-up to admire and capable of any music genre and SPL in a domestic environment one would care for - full range at that, and with headroom to spare. "
  You touch on something rarely mentioned I fully agree with. Pro gear just has much more headroom and effortless superb output. All I would consider for my own use is now Klipsch pro gear starting with at least a KI-904 or better or older versions at least as good as the KPT-456 or better. Some of my speaker buddies have Danleys and love them. It really boils down to what is most important. Sound or looks and here sound wins. Danleys are darned hard to find and so is Klipsch pro gear but the Klipsch does show up from time to time. I listen to a takeoff of the MWM bin from the MCM-1900 ( stock MWM is 40" deep mine is 60" deep same basic configuration though just bigger)  made so it goes down to an honest 27hz and with a Klipsch 402 horn and driver on top out to well past 18khz. This is a true two way all horn system and you just cant beat horns for best sound. It is why I recommended the Jubilee because it too is an all horn system and the gateway to superb sound.

After 15 yrs, speaker technology is still almost the same, although there may have been some advances in implementation brought about by research.

Well usually research is how advances are made :)

I'm a fan of the Classic Audio Loudspeakers and have a set of T-3s. They are 16 ohms, 98dB and go flat to 20Hz.  The midrange driver is field coil powered for less dynamic compression and employs a beryllium diaphragm with a Kapton suspension. Its first breakup is at 35KHz; as a result the speaker is detailed, fast and smooth.

 Also the bass got flabby/slow/less present.

@chilli42  One thing to be careful about in the bass department: 'tight' bass is a coloration brought on by the amplifier having excess damping of the woofer(s). Many audiophiles like it, but out in the real world its a very difficult thing to encounter! Another issue is standing wave; the most elegant solution I've seen is the use of a Distributed Bass Array which may have been what you were trying with the Rels. Did you place the Rels asymmetrically in your listening room?

@mahlman --

You touch on something rarely mentioned I fully agree with. Pro gear just has much more headroom and effortless superb output. All I would consider for my own use is now Klipsch pro gear starting with at least a KI-904 or better or older versions at least as good as the KPT-456 or better. Some of my speaker buddies have Danleys and love them. It really boils down to what is most important. Sound or looks and here sound wins. Danleys are darned hard to find and so is Klipsch pro gear but the Klipsch does show up from time to time. I listen to a takeoff of the MWM bin from the MCM-1900 ( stock MWM is 40" deep mine is 60" deep same basic configuration though just bigger) made so it goes down to an honest 27hz and with a Klipsch 402 horn and driver on top out to well past 18khz. This is a true two way all horn system and you just cant beat horns for best sound. It is why I recommended the Jubilee because it too is an all horn system and the gateway to superb sound.

Thanks for chiming in. Pro gear usually has that rugged and industrial look, and with amps and other electronics I actually tend to prefer that look; it’s just more "honest" with a functionally clean, understated and at times even elegant appearance (take the Crown Studio Reference or Macro Tech amps, as an example). With speakers I like it when they’re made of and actually looks like wood (i.e.: not lacquered to glossy death), but that comes expensive. I would though gladly and without any hesitation whatsoever go with the "ugly" pro speaker if it means better sound (and much cheaper at that), because as you say it’s what truly matters vs. mere appearance.

Klipsch pro gear has great offerings - the Jubilee’s among others have had my attention for a while. Going all-horn is a necessary step few are willing to take, but it makes a potential difference the majority will likely never face.

Pro gear is usually where the real innovations are made, like Danley’s Synergy horns. It’s arguably approaching the holy grail in sound reproduction as a single, phase coherent point source per channel - carefully summed by a closely placed, multitude of drivers - that covers down to where the subs take over. It’s brilliant, really.

@atmasphere --

Also the bass got flabby/slow/less present.

@chilli42 One thing to be careful about in the bass department: ’tight’ bass is a coloration brought on by the amplifier having excess damping of the woofer(s). Many audiophiles like it, but out in the real world its a very difficult thing to encounter! [...]

What’s really addressed by the OP here is a lack of coherency; the authentic fullness of bass reproduction that is to be implied by the quoted passage of you above (and that I agree with as something that doesn’t come across as "tight" per se), doesn’t distinguish itself incoherently from the rest of the frequency spectrum above, but rather it "flows" in organically. If that’s what the OP had actually heard - i.e.: named authentic fullness - he’d have known the difference and wouldn’t fault it.

Indeed, a specific term calls attention to itself from poster @chilli42’s description, namely "presence," or a lack thereof. One of the core characteristics of horn-loaded bass is exactly that: presence, and one that is wholly enveloping in a way the direct radiating bass, distributed array or not, won’t achieve in a similar fashion. What’s more, "flabby" and "slow" bass as an antithesis to "tight" is hardly a compelling trait as something associated with natural bass.

This is not about the age of speakers, and that’s not saying the OP should keep his current horn-hybrid speakers. On the contrary, I clearly feel he should replace them and patiently seek out an all-horn approach that will maintain high efficiency, but add in coherency. This has been done for decades by those sufficiently dedicated. What could be a further interesting addition though, and where the latest technological advancement comes in handy, is effectively emulating a point source and achieve coherency in the time domain as well.

@phusis Just to be clear, nowhere did I state that

What’s more, "flabby" and "slow" bass as an antithesis to "tight" is hardly a compelling trait as something associated with natural bass.

I simply pointed out that overdamped speakers often results in a phenomena known as 'tight bass'. I've heard it in stereos many times but have yet to encounter it in the real world.

One of the core characteristics of horn-loaded bass is exactly that: presence, and one that is wholly enveloping in a way the direct radiating bass, distributed array or not, won’t achieve in a similar fashion.

Horn loaded bass is a rare thing to hear- on account of needing a bass horn that is very long- 20 feet or more. Even audiophiles with a relatively wide open budget may find such size a bit daunting! But the issue that isn't solved by any bass system that originates in front of the listener is standing waves. Standing waves can't be solved by room correction either; if there is a standing wave causing a lack of bass at a certain frequency at the listening chair, you can put as much power as you like into it without significant change. But if you employ a distributed bass array the standing wave is corrected and you will have 'wholly enveloping' bass.