...I think the key here, when listening to recorded files of the SM7/VTB-1 combo on vocals lies in the consistant value of the SM7, more than the VTB-1...
...I have used the SM7 with a broad range of mic pres, and as long as the preamp has the "juice" (65dB +) to drive the SM7, there is a consistant quality of performance, mostly due to the design of this dynamic mic...
...on the other hand, condenser mics (IMHO) tend to respond with much more variation to different preamps, and tend to reveal more about the characteristics of each individual mic/preamp combo...the "tube" drive in the VTB-1 is much more critical when drivng a condenser than a high quality dynamic like the SM7...you will hear the "wooliness" much more quickly when dialing in more tube gain...
...the SM7's consistant performance/reliability is the gem in this combo...the VTB-1 simply offers up more than ample gain to let the SM7 deliver the goods...of course, that's just my take on the combination...