I personally love my Solarus (I have the fourty watt version). I can' t speak for other 60's Sunn amps from personal experience, but I would wager that it doesn't really matter that much.
The 1000S is probably the king s**t of the pre-70 guitar amps. I play guitar through my 2000S bass amp sometimes which is basically a 1000S without the reverb and vibrato (tremendous reverb and vibrato with the Solarus BTW) and it makes for a monster guitar amp.
But I think you are going to find that all of these amps (Solarus, 1000S, Sceptre, 100S etc.) are all going to be clean, clean clean with all the clean headroom you could want. you're going to be hard pressed to push them into distortion without deafening yourself first.
But my Solarus take peddles for that like a champ.
All of this is just my $ .02 though. There's others on here that know way more and that might disagree with what I've said here.