Speaker suggestions

Depends upon your particular prioritization of:
- Dynamics
- Imaging
- Frequency response
- Musicality vs. Accuracy

Personally for me dynamics is top of the list so I am drawn to horn speakers (Klipsch La Scala) on a low power tube amplification.  My personal tube favorites are Klipsch horns or the outstanding Devore O/96.

A used Vandersteen 2CE Signature II or the 3A Signature for $3000 or less. Purely design and made in the USA

Hey Sophie 999,

I have heard 3 different versions of the Tekton Double Impacts--standard, SE, and the Bill Dion (grannyring) drivers, crossovers, and wire upgraded standard DI's.  The SE's are pretty nice but cost $6000.  The standard DI's are not as sophisticated sounding as the SE's.  Bill's a VERY experience DIY guy and has maximized several speakers closer to their potential along with electronics.  He also makes the very fine Acoustic BBQ cables on Audiogon.  His DI speakers  are quite a bit better sounding than the SE version.  You can find the DI's more used for sale than before because Eric has come out with 2 new models that are supposed to be freakin' awesome and people are trading up.  The speakers are not show pieces, however.

I just heard today at a dealer a pair of ATC SCM40 V2 speaker that are built extremely well (albeit in England) and weigh in at 78 lbs. each although they are only 41" H, 9" W, and 9" deep.  They have a lively, impressive sound with very strong bass and magnificent mids.  You could find some used in your price range.  ATC makes many of the top studio's speakers and they are very accurate and punchy.  I came away very impressed.  I own VMPS RM40 BCSE MLS speakers that have 40" of ribbon drivers along with two 10" woofers per side plus a 10" passive radiator.  The VMPS speakers properly set up and adjusted are very tough to equal in clarity, transparency and good bass.  I also have a pair of Vapor Joule Blacks that are even more impressive, but very expensive.  You could find a pair of VMPS used and might love the sound.  RM2's, RM30's, or even RM40's used could be had.  The 40's and 30'd have been highly praised by several different reviewers.  The 40's are 240lbs. each, the 30's are 115 lbs. each, and the RM2's are about 120 lbs. each.  The drawback of them is the designer passed away several years ago.  VMPS is no longer in business but there is some very helpful people on Audio Circle that can lend help if you had problems down the road.  I've bought several different speakers trying to beat the VMPS sound for me, and have been very ineffective.

Bob

@OP, 
Are you near any dealers? Nothing beats auditioning speakers with your own ears.
Bob

Great suggestions. Thanks very much.

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. 

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.

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.

Best,
E

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).

My next speakers to hunt down are the Dali Zensors - try to hear them before buying any speakers though. They have clear sounding woofer and pleasantly transparent highs...They are Danish speakers - don't know where they are actually made, but there great speakers coming out that country.

Spatials would handle classical just fine; however, you'd want the Triode Master version of the M3. It was designed to work with 20w and below tube amps and has 12-16ohms!

Thanks for the suggestions.

Honestly, leave those speakers alone or sell them.

Monitor Audio Silver series. New or Used.
Also, consider room treatment.

Best,
E

Since you have a powerful Decware amp, have you considered talking to Steve at Decware about which of his speakers would work best?