If some company makes hardware for its own software, it can be expected it works fine with that software. It can be also expected it works not so nice with other software.
Mackie MCU can do almost everything a Control Surface can do with Sonar. If you do not like that, there is no reason to check for other solutions (for Sonar). But it will be informative in case you can explain what exactly you mean by "partial integrations" you have experienced.
Existing discussion for the same topic:
http://forum.cakewalk.com/FindPost/3555945 PS. It has less controls then MCU/X-Touch but it cost the same money as X-Touch. So far I have not see any comparisons, in terms of used hardware components quality, faders actual resolution (in X-Touch it is probably MIDI resolution) and smoothness during following automations, etc. Note that functionality in Sonar is irrelevant (obviously X-Touch will win because of the number of physical controls).
PSPS. Many people have already asked for affordable (! important, to avoid VS700 failure) surface from Tascam.