25 year old polk 2.3's will I hear an improvement?

I can't say I've made a similar upgrade, but can point out a few things:

1. I listened a lot to the Polks at the time they were out and always felt they were bass-heavy and shelved down in the highs. Keeping in mind I'm going with 20+ year old memory here, the Wilsons and the Krell speakers you mention would have quite a different tonal balance than what you might be used to. You really have to hear them, but then I think you'll see what I mean.

2. The Polk SDA speakers are definitely different than any of the other speakers mentioned in that they had that stereo dimensional array technology which sent out of phase signals from each speaker to eliminate some perceived flaw in typical stereo speakers (damned if I can remember the actual terms they used--maybe the signals eliminated crosstalk or something). The point is that they definitely sound different than most other speakers I listened to at the time; again, you'll have to hear those other speakers to determine whether you like the Polks' presentation better. I recall a lot of Polk SDA owners bought and have held on to these speakers because they are different.

3. Finally, while I think your room is fantastic, the way you have the Polks set up, up against a back wall, will likely not work at least for the Wilson speakers, which do better away from the wall (can't comment on the others, but do note that there are not that many speakers out there today that are intended to be placed close to the back wall).

Hopefully someone who has the SDAs or has sold them can comment more from actual experience; I just chimed in because I did hear them a lot when I first got into this hobby and have strong memories of them.

RCprince
Thank you for your helpful reply. Yes, the SDA's phase cancel the cross talk by sending a signal to block right speaker sound from coming to the left ear and vis versa, with the intention of creating a more realistic rendition of true stereo, allowing for the sound stage to be more expansive in both depth and width.
The Krells reportedly are designed with close to back wall placement in mind. But I have had that concern, since I do not have a dedicated room and cannot put speakers a third out into the room.

There is no correct or incorrect answer to your question. Here is my story. I owned the Polk SDA 2.3 speakers for a number of years myself. The upgrade bug finally caught up with me and I replaced the 2.3’s in 1999. I also was not able to audition or hear the speakers I purchased in my dedicated room. Bottom line is that although the new speakers were an improvement, I was amazed as to how good the 2.3’s actually sounded. The cost of diminishing returns enters into the formula. If you have the big bucks to spend for new speakers (I would guess at least $5000 new / less used) and you realize that there will be improvement, however most likely not to the extent you are imagining, go for it. Over all I was happy with the new speakers however the SDA 2.3 speakers do a lot correctly. Good luck!