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

Since you've already upgraded the tweeters, you might want to try upgrading the crossovers with high quality parts. You may find that to be all you need.

Merganser - you may be right. So far I have been chicken to do so, since I do not have the personal expertise, but I will probably go listen to at least a few systems that proclaim to be great in good settings and if they blow me away look for new speakers, if they dont then I will consider crossover upgrade. But I have heard that sometimes the upgrades dont work and they ruin the speakers - any truth to that?

a lot of sophia owners would crap if they heard how good your sda's sounded.

You should be careful--I had a project with the manufacturer and designer of my speakers where we replaced the crossover built inside my satellite speakers with an outboard crossover using much better quality parts (Hovland caps, Alpha Goertz chokes, WBT binding posts, better quality wiring) with the same values as the replaced parts. The result was not entirely to either my or the designer's liking, as the speaker, while far better in many respects, became almost unbearably bright. It took some redesign work and tweaking to get the sound where we liked it. So I would not discard the old parts until I was happy with the sound of the crossover with the new parts. You can get a different sound, but different isn't always better, at least IMHO.

Gammajo,
I replaced the 2.3's with a pair of Legacy Signature III speakers that I purchased new from Legacy. I noticed different mids and highs. They also seemed to be more open and lifted the veil. I'm about to put them up for sale as I now own a pair of Montana EPX speakers.