I have run the Signature Ming Da MC-7 into the 3205, and have also tried the ModWright SWL 9.0SE.
I like the slight power boost that the active preamp provides, but it needs to be very clean.
For this reason I thought the ModWright performed better than the Ming Da, which seemed to exaggerate the tube aspect of the 3205 sonic signature a bit, rather than stay neutral and get out of the way, and let the 3205 do its stuff (which is what the ModWright did)!
There are other clean active preamps out there that might be explored. Since I have no direct experience I will not suggest anything, but the bit of volume boost and dynamic boost that is provided by a good clean active preamp is not a bad thing with the 3205 (depending on speaker efficiency, of course). Just my two cents. Bill's 3205 has a very musical and clean sound, and what I would be careful about would be disturbing that balance with an overly tubey preamp. Also, with a tube preamp, tube rolling can make a considerable difference.
Bill can likely mod the AN M2 (I believe, check with him) to improve its output, without disturbing its overall sound.
Last, but not least, my experience with my ASL Hurricanes has been that the 6SN7 tube variants and makers are associated with significant differences in the sound provided by that tube. I have found many of the Sylvania's to be highly microphonic, even though being desired chrome dome types and other valuable early versions. If going with NOS 6SN7s it is a good idea to have then evaluated for microphonics. What I have read about the AN M2 suggests that it should provide a very clean sound, somewhat similar to the ModWright, and be an excellent augment to the 3205 (once set up properly). Let us know how this works out !
Bill C