Speaker suggestions


I know this is a difficult question to answer, but any opinions are welcome.

Here is my situation. I listen mostly to pop and classical, including many symphonies. About 15x25 feet (5x8m) untreated room. 20wpc Decware amp currently driving 15 y/o LSI 15 polks. Polks are doing fine, nothing wrong with them. I am the 2nd owner.

I am considering an upgrade to my speakers. Would like to have full (or near full) range speakers, no sub, strongly prefer something made (assembled, not just designed) in the US, with 2-3k budget.

One option is to refurb/upgrade the Polks. About 1k gets me new premium crossover, new damping material, full inspection, and cleaning with some cosmetic finish work at a local well regarded audio shop.

The other option is buying something new. I plan to keep the system for at least 15-20 years, so need something well built, with solid fit/finish, and good internal electronics so I do not need to recap for at least 15 years.

Prefer new but will consider lightly used option if find something specific I like.

Have been looking lately at Tecton DI and Impact towers. Some posts mentioned that they do not measure very well, but I did not see any charts on the forums or on their site. Mostly great user reviews,
Other options are Ascend Acoustics Sierra towers, Klipsch Reference, SVS ultra towers. I think those are all US made. Spatial audio has great reviews, but not sure how well they handle complex classical music. 

Can you please provide comments/suggestions? Any other options worth considering. I am not much of DIY person.

Thanks much.
Only reference quality, full range tower under $4000 is the Philharmonic Phil 3. It is 88dB efficient from 30Hz up, same as your Polk’s.   
The Sierra Tower (especially with the RAAL upgrade, making it ~$2800) is probably one of the 5 best towers under $4500. It however is not full range (34hz). A subwoofer would still be recommended in my opinion. 

Stereophile has measured Tekton. Due to its tweeter arrangement, it has a very narrow sweet point in the vertical realm, meaning going from sitting upright to slouching causes a decent change. However, they are pretty accurate with good imaging/soundstage. I would still take the Sierra+RAAL over them though. 
You could just keep your speakers and spend say $1000 in room treatment (<$500 if DIY).
I heard the Dali's. They sound like they measure, bright!

However, if you like lower volume listening, a good deal.

If used with room correction, the EQ will correct for that.

No doubt the amp/speaker match is very important for quality sound. Rather than suggesting my favorite speaker like most posters do, I'll make a comment.

Due to the parameters you mention in your post, a higher sensitivity speaker will be better.

Classical can be some of the most dynamic music available. I seriously doubt your current amp/speaker match can deliver that type of dynamic range. Compounding this issue is that the room is fairly large.

A speaker with a sensitivity of ~95db or higher on the 20 watt tube amp will take you to the concert. To get that type of dynamic range on the Polks would require at least 100wpc.

Ascend Sierra RAAL tower speakers are fantastic for the money. David is a great guy too. I had them for about 3 years and enjoyed every moment with them. They had no trouble with a tube amp but mine put out 48W per channel rather than 20W. They aren't power hungry but they aren't the most efficient either. 

Midrange and top end is fantastic, particularly with the RAAL ribbon tweeters. Bass was a bit lacking to me however. I would suggest a sub with these speakers.