Front-end disclosure: no experience with the C1s.
That said... the Smart 845 only puts out 25W. I would think that is not nearly enough to drive an 86dB speaker, even if the impedance curve is relatively benign (i.e. at nominal 4 ohms - it appears from the Stereophile measurements they don't go below that). Personally, I would expect the speakers to suck too much life out of the amps. My personal experience with similar load speakers and tube amps would suggest that for decent dynamic range and clean sound, one would be happier with a fair bit more power. If you want high-power triode tubes, you could try something like VTL MB250s. I would be hesitant to try to drive those speakers with SETs.
Perhaps a C1 owner can chime in.
That said... the Smart 845 only puts out 25W. I would think that is not nearly enough to drive an 86dB speaker, even if the impedance curve is relatively benign (i.e. at nominal 4 ohms - it appears from the Stereophile measurements they don't go below that). Personally, I would expect the speakers to suck too much life out of the amps. My personal experience with similar load speakers and tube amps would suggest that for decent dynamic range and clean sound, one would be happier with a fair bit more power. If you want high-power triode tubes, you could try something like VTL MB250s. I would be hesitant to try to drive those speakers with SETs.
Perhaps a C1 owner can chime in.