Well i can relate to the OP's situation since i have the same issue with my Brent Mason. It's more complicated than just turning the tone down. I love my BM but i can't use it on every amp, but I definitely use the 'hi-fi" tone as an advantage sometimes. I'd imagine that if I only had that one guitar, eeesh....but...that's why you don't keep only one.
I mean no offense, but please understand that my point was to not overthink things. Many times it really is simple. And built into the design of the instrument itself. The OP stated that the frequencies on his new guitar seemed too bright, and there's a built-in cure for that right inside the guitar - the tone knob. It seems silly to me that people don't use it more.
FWIW, I've got a lot of guitars, too, some for practical reasons, some for sentimental reasons, and some for the sheer hell of it. But on all of them I'm aware of the range of tones/sounds I can get from them and know how to tweak my playing or how to use the instrument differently to get the sounds I want.
OP - apart from using what's already there to control the tone, there are also a ton of tweaks and mods that can be made to alter the guitar's overall sound - thicker picks, picks with rounded edges, picks made of softer materials, thicker strings, changing from steel core to nickel-based strings, lowering the pickup height, changing the bridge saddle material, changing the way you actually fret your notes, changing capacitors on volume/tone pots, lowering the treble / presence on an amp, using longer instrument cables with a lot of resistance... all of those things can lessen the brightness of a guitar with little or no cost.
And don't get me started on the importance of using the volume knob...