Speaker for McIntosh setup

B&W is the classic match.

JBL L200.

Having had McIntosh equipment in the past, B&W would be a good match as mentioned already. I have not heard the new JBL’s, but in the old L100’s were good matches and I would bet the new versions would be just fine also. 

Vintage speakers to go with your vintage gear or new?

If vintage, the aforementioned JBLs (L100s, L112s, L166s, L300s) would be good matches, and you can probably find some nice examples relatively easily and stay within your budget).

If new, you’ve lots of choices. Depends on your taste. If I had a big room to fill, I’d seriously listen to the new Cornwall IVs. A bit over your budget, but the reviews are pretty good.

Really anything neutral or even a touch bright will be fine. 
I would stay away from dark speakers with Mac gear. 

Newt

james633,
I agree with you. Many speakers will work well and sound great, but stay away from dark sounding speakers. I would never team it with B&W, but then I don't like their speakers.

Focal Electra 1038 BE
Focal and McIntosh pair very well

https://www.canuckaudiomart.com/details/649740849-focal-electra-1038-be-in-very-good-condition-funct...

So I have heard a lot of good review of the new Klipsch Heritage line.  Would the Heresy IV or the Forte IV work well with these older McIntosh units?

I can’t answer you question directly but I can give some klipsch Mac input. 
I use Klipsch RP8000F in my home theater but when I broke them in I hooked them up to my two channel rig which has a MC462. The MC462 and the RP8000F really made me question a lot of things. It sounded plain out good. The mids of the klipsch lack the presents and last bit of detail (but not bad) but the highs were great. The bass was deep but also lacked the last bit of detail. All in all way better than a $1000 speaker should sound in my mind. 
I was a bit dumb founded as how such a cheap speaker with a box that was super hollow sounded... well good. Interesting for sure. But who would hook up a $1000 speaker to $15,000 worth of electronics. 
I also demoed the Cornwall IV on a McIntosh 7200 integrated. It sounded so so to me with kind of odd bass that did not seem to blend well with the mids. It could have been the room etc. I need to give them another try at a different dealer/room. I have two in town. The highs were very nice on the Cornwall iv Mac setup though. 

Redwood, 
I have a new pair of Heresy's with my Mac 240 and I am completely enthralled. For me the set up just sounds like a perfect fit. I added an SVS PB 2000 and that really rounded everything out. This is the sound I've been chasing for so long now. Mostly listen to jazz and rock of all kinds. I used to sell TDL transmission lines and owned three pair over the years. Great neutral sounding speaker, harder to drive, fickle with amplification and set up. But these Klipsch Heresy's have really opened up my listening experience. I know there are a couple camps when it comes to horn loaded drivers and I was a hold out for a very long time. I picked mine up from Audio Classics in NY. They were great to work with and since I had about a 6 hour drive to get to them, Audio Classics had several set up for my listening session. If you are anywhere near them do yourself a favor and make an appointment with Ryan. 

I have found that really good components can get the most out of decent speakers. But of course to get the most out of your system requires complimentary quality speakers. I have run some $3K speakers on $30K of electronics for years. The speakers were ribbon so they really did perform over there cost... but ultimately I wasn’t betting the most out of my system.

"Note: The system is in a large great room."

My advice would be to make sure you get speakers that are large enough. I have heard great speakers sound not good because they were in rooms too large for them. You lose bass and without the low end it sounds off. This was in a double story great room. You may end up needing a sub so consider that in the budget.

I run Focal with my McIntosh and love it.

I've been happy with Sonus faber speakers - and at $5k the Sonneto V is right in your price range.

McIntosh is better paired with neutral/fast sounding rather than warm/slow speakers. So, B&W, Dynaudio, Focal, Raidho, etc will be generally good matches.  

Surprised that no one has mentioned Martin Logan.

Despite what others may say I have never care much for B&W, Sonus Faber, or Focal on McIntosh and I am surprised there are so many enthusiastic supporters of those combos....

Used to own a pair of Vantages, the current equivalent around $5k would be first on my list.

The users recommending Klipsch are on the right track as well, especially given the vintage of the OP's gear.

But for $5K you could probably find a used pair of Summit X's or something like that and be doing pretty well. The separate powered/active sub eliminates having to worry about the otherwise "wooly" sounding bass Mac has, so the amps are just handling the mid and upper frequencies.

McIntosh XR100