Speaker recomendation

Tls any speaker that is 91 or 92 db is efficient, sure it may not be 96db or 101 db but that is still a high efficiency design compared with most of the industry's 85-89 db figures. 

Looked up the Athenas, although that speaker is more electrically efficient, you have one woofer with a much more limited amount of deep bass, the greater the room size the more bass energy you would need. The Legacy uses 2 12 inch long throw woofers with a 3db down point of 18hz so in reality would be much better suited to the task of driving this room.

The OP should see if he can locate a pair and take a listen.

Dave and Troy
Audio Doctor NJ

Retired now, but worked in the audio industry for over 25 years. Remember that average speaker sensitivity was 88-90db, with 85db considered to be low and 95db being high. The industry average may have shifted, I don't know, however the relationship of amp power and speaker sensitivity to achieve volume and dynamic range remains the same.

During that time, I was fortunate to be exposed to so many different products and setups. Heard Legacy speakers a few times and had a friend with a pair. Did they sound ok, sure, but never seem to be special, the goose bumps or making hair stand up thing. Some other listening experiences were impressionable and hard to forget. And please understand, this is just my opinion.

As far as the "having a bigger hammer" thing, I'm sure that appeals to many, but not me. I prefer quality over quantity. I never get focused on bass and treble, like so many do. I want the best midrange with a good balance of everything else. Basically, a speaker that doesn't have a strong point, but does everything well.

Absolutely, the OP needs to take a listen, but to as many speakers as he can.

And finally a thought for the day.

“I must go in, the fog is rising.”  -  Emily Dickinson

And a joke for the day.

What did the egomaniac say when leaving his friend's house?

Don't tell me goodbye after I say goodbye to you!!

Audiotroy doesn't bother me, because I take his recommendations with a grain of salt. If he recommends something that sparks my interest, I go listen to the component with my owns ears. I did that for speakers that he recommended and recently with T+A electronics. I listened to the T+A  PA 3100 HV driving Magico A3s. Based on that experience I don't think the PA 3100 HV is anything special. Listening always puts everything into perspective.  

Meanwhile, back at The Topic...

IMHO, if I had a room that big and $10-15K for amps and speakers, I would probably try this:  I would call John Strohbeen at Ohm Acoustics, and ask if the Walsh 5000 would be able to work in that large space.  If so, that's $6600 for the speakers.  If your space is too big for them, John will tell you the truth.  They work well with reflective surfaces, so you may not have to do as much to treat the room and those windows as you might with more directional speakers.  They also have several frequency band output level controls, which might be especially helpful in your situation.  For an amp, lots of clean power is the key.  I would go for the Arion Audio HS-500 monoblocks, which are tube/Class D hybrid designs that output 500 watts each.  I have heard them with both Nola speakers and Magicos, and they are great amps, IMHO.  I had the RS-500 monoblocks (with solid state input stage) for a while and thought they were also pretty good.  But the hybrids are better sounding and within your budget.  That's another $6300 for the pair.  That leaves you a bit left over for some decent power and speaker cables.  YMMV, of course, but both of these products are sold direct with in-home trial periods.

Harbeth 30.2 fantastic for classical music and jazz.   I'd go with a SS Amp and pre or an integrated ss!  I love McIntosh with Harbeth!