Guys, I just got back from a practice using my SA200/NV215, and I was very impressed. I think I have explored the volume limits of this combination, and I officially label it "more than enough" in the volume department.
With all tone controls set at noon (BTW, I'm not sure what the "flat" setting is on this just yet), the tone is very full, and what I would call "new vintage." Just as Jim Bergantino's NV-series cabs have a vintage vibe with some modern clarity, the SA200 (again, set with all knobs straight up) sounded full, warm, yet clear, harmonically rich, and with good articulation. Of course, perhaps the SA200 is, in fact, 100% transparent, and I was just hearing the NV215 for what it really is!

I'd say it's more likely that these two products just work really well with each other and play to the other's strong suit.
As I moved into the tone controls, I was again struck by the fact that they were plenty powerful (though not overpowering), but that you really almost couldn't dial in a bad tone. One of my favorite tones (I was going for a rich, full, yet "modern" articulate tone with good clarity but still a sense of "girth") came from boosting the Top (6 kHz) and the Treble (3 kHz) slightly, and from cutting the Bass (80 Hz) to about 10:00 and boosting the Bottom (40 Hz) to about 2:00. This might seem like the opposite of what to do, but this setting on the Bass and Bottom yielded an extremely tight and punchy tone (with absolutely no bloating or boominess at all), while still maintaining a balanced, forceful low end. My drummer commented that this was the best that he has heard me sound (and trust me, he's heard me play through plenty of rigs!

).
Roger is clearly going for a wide range of usable clean tones, and this amp has excellent headroom, with tube compression/saturation only seeming to occur at the more extreme settings. The Fat switch ends up being even more flexible than I had expected. My initial thoughts were that it would be basically an "on/off" switch, in that it would allow you to choose tone A or tone B. But, used in conjunction with the gain controls (and please take note that the preamp section has individual Gain and Volume controls in addition to the Master volume control governing the final output gain) and EQ, the Clean/Fat switch allows a remarkable number of adittional usable tones. With the Fat control engaged, and the Gain knob cranked up, you can dial in some overdrive, though it does not get to "buzzsaw" levels. Like everything that Roger seems to do, even the range of overdriven tones seemed very "musical" (less like an "effect" and more of an inherent part of your tone).
As for the basses, I brought along my Skjold Custom 5, my Sadowsky 25th Anniversary 24F 5, and my newly arrived (but pre-owned) Fodera Emperor Deluxe. The Skjold is desperately in need of new strings, but it's my main gigging bass right now, and I used it to get an initial feel for the amp. Switching to the Sadowsky, I was truly amazed. I had never heard my Sadowsky bass sound so good (well, except for in my basement, by myself, through this very same rig, but that wasn't as loud, nor was it with a band). As much as I love my 25th Anniversary instrument, the SA200/NV215 has provided me with new respect for this fine instrument. I do agree with my drummer that this is probably the best that I have sounded (or at least as good as the best I have achieved in the past). Of course, I am still on the "honeymoon", but I honestly don't recall sounding better, nor has my 24F 5 ever sounded better. The Fodera also sounded great through this rig, and I am convinced that it is a "keeper", but the 24F 5 really stole the show with this rig.
Forgive me for not waiting until I had a dozen or so gigs with this rig under my belt, but this is an exciting product (at least I think it is), and several people have asked me to share my thoughts sooner as opposed to later. Again, I will update my "findings" as opportunity allows.
For those of you familiar with Roger Sadowsky, it should go without saying that I am in no way being influenced by he or his company to say one thing or the other regarding this amp. If it seems like I am being inordinately praising of the SA200, it's because I am honestly very impressed. Sure, it's not going to be for everybody, but I'm sure glad that I have mine.
Take care, Tom.