it should be neither thin, dark or shrill (interesting combination of comments on your part, BTW, I can't say I've every had an amp that did all 3 of these simultaneously!).
Lol.... Yeah, those are kind of contradictory descriptions, aren't they? Wasn't specific enough: shrill sounding when the definition's up, unpleasantly dark when the reactance is up, and generally kind of flat-sounding, not so much thin. There's a certain mid-rangey smoothness and lack of definition to it (and the definition knob increases that definition but not in what I find to be a pleasant way). I'd really prefer something with more snap to it, but snap that's both clean and with a great deal of presence and that's aurally pleasing to me in the same way Jerry's snappy guitar sound is to my ear. So I was thinking just getting a power section that's similar to an old blackface Fender Twin might solve my problem, or that it may be time to try a Mac. When it comes down to it, it's not that I want more mids, highs, or lows. Just that I want it to sound right to me. It may also be the Commonwealth. I know that it's a pretty bassy speaker. But I dunno... when I switched to the commonwealth from an Emi RWB it was a huge improvement to the sound, so I'm not inclined to think it's the speaker.
Similar thing happened when I went to buy a bass amp back when I was playing bass. Plugged into a WT800 and plugged into an EA iAmp Pro, and I just didn't like the way the Eden sounded. The EA sounded a million times better to me, so I bought that one. Which is crazy, I know -- Eden makes great gear, Phil uses it, etc. But I have pretty sensitive hearing and it's really just taste, which is hard to predict or cater to.
I actually read your V300 settings a while back in a different thread, and I've tried the 10 for reactance and 3 for definition, and they just don't sound right to my ear anymore than the rest of the amp sounds "right" at other settings. Sound is such a subjective thing -- in the end, all I'm trying to do (all we're all trying to do) with all this gear is elicit an emotionally pleasing response.
But, having played with the reactance and definition knobs in different positions, I've just been turning them both off all the way. It sounds worse to me with them on, so my thinking is that minimizing damage might be the best course of action. So I leave 'em off. That may be a poor choice, and if y'all think it is, I'd love to be able to try out any recommendations you have.
Settings on SMS are bright switch on middle position, treble at 10, mids at 4-6 depending, and bass all the way off or close to all the way off.
Edit: I realize that doesn't leave a lot of room for recommendations with the power amp I currently have (though I'm open to any and all), so it kind of brings me back to my initial question... thinking a different power amp may be the answer to this tone issue for me. If anyone has suggestions I'm open. My ideal amp would just be getting a fuckin MC2300 already, or a 2100 or a 2150 would also be fine. That being said, though, I'd prefer something new because there are no decent electronics repair places around here, and with vintage electronic gear I don't doubt that I'll run into more technical issues than with newer stuff. Got some nice bass gear to sell (lol) to fund that particular project, so let's say, for the sake of opening up suggestions, that money is no object up to around the $2000 line. I'd also really like to be able to buy something that I could go and hear and play through in person first -- personal recommendations are only so useful.