The best speakers to pair with McIntosh MA7000 ?

ATC 19s or 20s. They will really dig out the detail in your music.

Match the speakers to your room size.

I own the MA6900. Though I have not heard the 7000, I am told it is identical, except for the additional power, more I/O choices, and updated cosmetics. I have paired the MA6900 with several Sonus Fabers to excellent results. I currently own the Grand Pianos (I like a laid back sound). Also worked well with Vienna Accoustics. Pairing the MA6900 as part of a more dynamic system (B&W Mark IIs) worked worked well too. It's a versatile amp. And, because it is a favorite of many stereo stores, you should be able to audition it or the MA6900 with several speakers relatively easily.

I also own the MA-6900, and have found the combination of a pair of Kef 201/2s and a Rel B3 to be absolutely heavenly. I didn't like the pairing as much with the Dali Helicon 400s I tried, but loved the Totem Mani 2s as well.
Enjoy that awesome amp!

I replaced a Levinson 383 with the MA7000. My system also includes Theil 2.4's and a Sim Supernova CD player. These items compliment each other quite well. The 2.4's are very revealing, the MA7000's smooth and powerful sound is a perfect match. The amp seems to have limitless power and is very dynamic. I also tried the MCD500 CD player which has slightly better detail and midrange than the Supernova.