Well, I have the RP010B, but the reviews and posts here from a few years back talk about several of the smaller ones, like the RPX38 (formerly the RPX35). I have not heard the smaller ones. I went to Rudistor after having glare/fatigue in the highs with several solid state amps,
and Rudi claims that his amps are tubey-sounding, and it was true for me. Mine is warmer than my tube amps, but like I said has great tight controlled friendly bass. Stereophile and some other mags mentioned them over the years.
I have tried a few other solid state amps from well known names, and I like the Rudi amps the best. I too am very annoyed by shrillness or glare. The Rudistor was the only amp that could deal with glare on my old Sony bass-light R10s.
I like my amp a lot with Hifiman, Mr. Speakers Ether, Grado, and Audeze.