We used this -
https://www.renegadelabs.com/products/m3gxt.html - for monitoring 5.1 on Media Composer on last big sport job I did. Worked well - takes SDI from MC IO and has one volume knob but various configs. We used 5.1 / 2.0 folddown mainly (we are mostly just on-passing truck output).
Also maybe look at the upmixer plug-ins for MC before you go full bore mixing in ProTools? We had the linear accoustic one, but there's others. They can just excite your 2.0 music / effects out to 5.1 knowing it should give a transparent folddown to 2.0.