I think it's got more sizzle than the SMS CTP (I don't like calling the "CTP" then "SMS" because both the CTP and the Spec are SMS but I digress).
The story I always tell is that I got the CTP, then a few weeks later I played my buddy's vintage 65 TR with gray D-120's and I'd never heard that sound before. Better than my Twin reissue (even when plugged into JBL's), better than my FYD TRP, and better than the CTP. It had character to the tone, some sizzle, but was so clean. And I don't mean "clean" like "it doesn't overdrive at all;" I mean "clean" like it was clear, airy, assertive, etc. Therefore I took a chance on the Spectrum.
Then when I got the Spec, I got that sound again. It definitely overdrives around 7 but it's clear, hi-fi, etc. I don't have enough superlatives in my vocabulary for it.
I think the high voltage and the spring reverb make a huge difference over the CTP. Like, HUGE. I sold my CTP basically immediately after I got my Spec, and I finally sold my FYD a month or so ago. The Spec is everything I need.
TB Tribute Custom Clone
Sarno Buffer
OBEL
Sarno Spectrum
KSR PA-100R
D-120 2x2