CR and FF800 playing nicely together here.
For up to 4 phones mixes CR + ASIO direct monitoring enabled (you have to do it in TotalMix as well as in Cubase) is extremely convenient.
If you need more than that, TotalMix offers up to 14 independent stereo mixes (think UFX even 15) - more than will ever make sense, never used more than 6.
Looking for a while myself to get myself an UFX because of TotalMix FX. Making use of the UFX’ FX would mean to use TotalMix FX instead of CR or using some kind of hybrid setting like cue sends from Cubase plus your singer with a little reverb or so from the Fireface via TotalMix.