Here is my impression on "Studio Reference".
I had been demoed SR several times but this is the first time with perfect seal. The first thing that I notice is that trebles are extended further that standard model. Trebles rolloff that many people consider it to be a weak point of MH335DW is now much better. The other area that I notice is bass. SR give you better resolution in sub bass region. The quality of bass improve while the quantity of bass is pretty similar to standard version. Soundstage is pretty much the same. Mids are still the epic of SR but the improvement of trebles make it feel less mid forward.
Overall I feel that SR is quite an improvement over MH335DW.