I used to own the BAT VK-30SE. It worked well with all of the power amps I tired with it. Pass Labs X-250, old Kinergetics KBA-75, Counterpoint SA-220, Graaf 5050 tube amp, etc. Not sure how the 31SE compares to the 30SE but overall I perferred other preamps to the 30SE for dynamics.
Happy Listening.
Happy Listening.