Welcome to the club, John!
What do you like about going into the Sansamp first? What elements of it do you use?
So the Fender Cab is relatively new. First I had just a PA, then a Bass head, and now the head and cab. The Sansamp was best for the PA as a full Amp Emulator. The Bass head into the PA speaker, the sansamp actually didn't improve the sound either going in first or through the effects loop, so I stopped using it for a while.
With the head and cab, the Sansamp once again sounds really good, and I have it on all the time now. I haven't experimented going through the effects loop with this setup. I did try bypassing the Hartke pre entirely and just run direct in to the effects return. That didn't sound as warm and tube like to me and I switched back to pedal direct to amp input.
I will try the effects loop and let you know. In general I keep the Hartke settings flat (2-10-2) and use the VT for EQ and Drive. I keep the character setting 12 or below which is closest to the SVT and Fat Tube Styles in the manual. High Character and Drive can be really grating, and High Charac low drive is not really a good rock style for me.
I have the Deluxe with 6 presets so I always have one of the presets with my standard sound, but increased level to act as a boost.
I'm in a three piece so I really want a Ramones, Green Day solid continuous eighth note rock bass and I definitely get this with the VT pedal on the Hartke and Rumble rig. Without the pedal it doesn't sound as rockish. We have grungier stuff and the VT Deluxe 6 presets help me switch the sound up to give greater contrast between parts of the song.