Folks, I won't begin by writing about PRS amps. Reason is, I don't have one, but have PRS guitars. I have a bunch of other companies' amps, and several home-rolled by tubed circuit designers. I was trained in jazz but love all kinds of music. Wildly varying tones of distortion and color are worthwhile, besides those Glorious Cleans, but the best tones from my experience involve a foundational, "clean" tone first. You can always add distortion, squash the frequencies and "EQ" your way to perfection manipulating the tonal eccentricities and attributes of the speaker, amp and pre-amp sections, speaker(s), speaker enclosure, etc. A great clean tonal range is a thing of rare, sonic bliss. I'm convinced that tonal range actually makes us happier human beings...so does rock and "purple haze," but they can get tiresome after awhile, yes?
I'll start by commending Leo Fender as we all should, for his early (Fender) Cleans. They range from a relatively quiet, smooth clean in the low-watters like the Tweeds, Champs, Deluxes, Princetons, etc. to the piercing cleans of the 60s, 70s and 80s Twins, "ultra-linear" designs up to the Big Iron Fender 140 (I have one, quite marvelous but a bit sterile, IMHO, add pedals) from 1989 and a wide variety of tubed, hybrid and solid state models created more by the marketing department than out of musicians' needs and wants. And sadly, as experts will admit, hardly any two birds of the same feather, such as two Deluxes, truly sound identical. They "tend" to do certain things with certain tubes of a certain age amplifying certain speakers and enclosures; the similarities become less distinct when you start playing around with different tubes, capacitors, resistors, speakers, cabs, etc. This is why Fender purportedly searches for "ideal" Tweeds, Brown and Blackfaces, and then builds reissue designs to sound like those ideal amp examples.
Next, the point I really want to bring out, all amps have their own versions of clean if played at gain ranges so low the tubes are hardly working, much less tending towards saturation and overdrive. (Ideally, the power and pre-amp signals will come from tubes, exceptions being things like the Fender Jazzmaster Ultralight, which very sadly is no longer being made.) I came back into guitar-playing a few years ago after many years away, seeing Line 6 pushing something they called the Vetta which offered credible emulation of other amps, many of which I'd never heard or played. It seemed like a godsend; I wanted the flexibility of buying one but "hearing" and broadcasting many amps inside. Their PODs and fairly amazing DT50 amp continue in that vein.
My latest example of another Clean is just so amazing I wanted to start this thread. It's a Mesa/Boogie Royal Atlantic RA-100. I can't really do justice to the splendid variety of Cleans it has available, but color me amazed and in awe. The designer has actually made the master volume setting meaningful; you can dime the Master and get some great cleans tweaking the "Gain" as you would expect, BUT you can actually thicken and massage the clean tone to new sounds by reducing the Master and raising the Gain. I'm probably distorting the tone somewhat raising the overall volumes with either the Master or the Gain, but they still sound relatively Clean, just hugely enriched or narrowed.
People say great things about a wide variety of thicker, juicier Cleans from today's 65Amps, Dr. Z, Fender, my favorite home-brewers Dave Lancaster of Lancaster Amplification and Paul Sanchez of Red Iron Amps, the DT50 (and purportedly, DT25) by Line 6 in triode mode and many others. What amps (tubes, speakers, etc.) produce your favorite Clean tonal ranges?