Advice from Audiogon family - best speaker $3k-$4k

OP,

Are you looking to replace your 804s or speakers for a 2nd system? 

If you can wait until Sheila Berdan is up and running in her new Seattle-area location, she is an Eminent Technology dealer. The ET LFT-8b has gotten great reviews (especially in the UK, but also by Robert E. Greene in The Absolute Sound, and by Harry Weisfeld of VPI, who declared the $2499/pr LFT-8b to possess the best midrange he has ever heard). Too bad it cost $501 below your minimum budget ;-) .

Brooks Berdan thought (R.I.P.) very highly of the ET magnetic-planar speaker line, choosing it as the planar speaker line over Magnepan for his shop (along with QUAD ESL's, and Wilson and Vandersteen box designs). I have both (Magneplanar Tympani T-IVa, and both LFT-4 and LFT-8b's), buying the LFT-8b after hearing it in the shop. For some reason U.S.A. audiophiles continue to ignore this great speaker value.

Unlike Maggies---whose low impedance characteristics prefer a solid state amp, the LFT-8b is an easy 8 ohm load, the magnetic-planar panel itself (which sits atop a sealed 8" dynamic woofer for 180Hz down) 11 ohms, great for tube amps. Two pair of binding posts---one for the m-p panel (housing a true push-pull magnetic midrange driver and ribbon tweeter, unlike the single ended drivers in the similarly-priced Maggie 1.7i), the other for the woofer---makes bi-amping or bi-wiring easy.

What sound are you looking for exactly?  Sf and B&W are polar opposites as others have mentioned, especially the 800 series B&W.  I've owned both and love the older B&W sound, 800 series are just too bright for my liking. 

At 3-4k you can get used Sf Sonettos and Sf Cremonas, both are exceptionally smooth speakers that are a bit shy on the bass.  They wont be nearly as detailed as your 804s, and with a mac tube pre they might be a little too smooth.  Personally I found that combo a bit too smooth for enjoyment.  The higher end Olympicas are much more detailed and made for a better match for mac tube gear (I run C47 w/ mc275 monos).  

Personally I find Focal to be a great match with McIntosh tube gear.  I've heard the Focal Aria 938 w/ a MA252 and it was an excellent combo.  Like the B&W speakers, I find the Aria line to be too bright but the tube front end rolled it off just enough to be not annoying.  I currently have the Kanta 2s and extremely pleased with them paired to my mcintosh stack.  

Now if you want something completely different from the B&W speakers, try Kef.  Their R series at that price point as very neutral and produce a huge sound stage.  I've heard the R11s on a MA252 plenty of times and it's a great combo.  

You should tell us what music you're listening.

I don’t want a bright speaker.  I like warm, but not muddy.  I need bass and detail.  I don’t see adding a sub with this system. 
I am not opposed moving the 804s and getting a different speaker for the main listening room. I have always wanted a of Maggies.