This was also an issue for me when upgrading to the Nexus line. Strangely enough I couldn't get an answer from Pioneer about the sound quality of the master tempo, not here or on forums nor in direct contact with them.
The only time I played around with the XDJ 1000 the first thing I tried out was the master tempo. I can assure you it's way better than the 850 but can't confirm it's on Nexus level.