The Premier 12 looks pretty similar to the one I linked, with a higher output impedance. The Eico looks quite colorful. Impressive scale on the tone controls. All three have relatively high bass distortion, the Eico especially. If you like the sound these amps are giving you, I can see why you would feel something is missing with most Solid State designs. Maybe there's a harmonic distortion EQ you could engage to emulate the tube performance in an SS amp but fine tuning that curve vs. output (since the distortion varies with power and frequency) sounds like a nightmare.
What speakers do you use? Is this only two channel and music or is it also put to use for home theater purposes?
I currently use them on a variety of speakers. I just sold my Thiel 3.7s - Jim Thiel's last flagship speaker - and believe it or not I actually loved how they sounded when I occasionally substituted the tiny 14W Eico amp (I don't tend to play music really loud). Currently using the slightly smaller Thiel 2.7s, a bit less sensitive, probably similar impedance characteristics. Also, Spendor S3/5s, an older pair of Thiel 02s, Waveform Mach MC monitors, Hales Transcendence monitors. I've used the amps on a large variety of speakers at home, including floor standing speakers like Von Scheikert VR 4 Gen2, Hales Transcendence 5, various Audio Physic speakers, bigger Thiel speakers (CS6), and many others.
The reason I have stuck with the Premier 12s is that they seem to give some of that "tube sound" I like, but with very little penalty in the bass region.
That is, bass doesn't get all flubby, loose - every speaker I've ever used on them, no matter how demanding the load, has given me taught, well controlled bass, even if the sound over-all is a tiny bit thickened.
AND I used both those amps on my MBL 121 Radialstrahler! These are quite a demanding speaker, similar specs to the bigger models at 81dB sensitivity, and as Atkinson wrote in his measurements of the big model "demand a good, high-powered amplifier rated at 4 ohms to give of its best, especially as there is a current-hungry combination of 3.8 ohms and –51° electrical phase angle at 37Hz."
So, going on specs and the recommendations of the typical objectivity-accuracy oriented audiophile/engineer, you would not go using an underpowered, reactive amp like the Eico 81. And yet, I tried it and it proved to be my favorite combination. The sound retains a sense of brilliance and aliveness, yet thickens a bit more making it sound bigger and richer, and the bass I think is less controlled by the Eico - but the
subjective effect isn't an obvious "sloppiness" but rather it sounds like the bass is richer and goes deeper - it makes the little speaker sound even bigger then it normally does.
Fun stuff. (At least, to me).