Eddie Current EC/SS. It's an odd find in the solid state world, but it matches Grado's very well.
Classic Rock, Blues, Psychedelic Rock, Instrumental Rock, all that sort of stuff. The heavy hitters of my listening is groups such as Beatles, Grateful Dead, Jeff Beck, Pink Floyd, etc and etc.
I love the intensity too, but there's only so far it can be pushed. To my ears, RS-1's are unbearably bright. I may have sensitive ears in the upper midrange, because those who loved the SR225's seem to love the RS-1's even more.
Tube amps were Zana Deux, a custom built Millet, and a Raptor. SS amps were a MisterX XP (or something along those lines, I forgot I had tried one), EC/SS, Original Audio Master, and my various home receivers.
Tube amps are on odd creature. The Zana Deux was one of the best amps I've ever heard. It requires a hefty source, but I absolutely loved it. So expensive

, but it changes the sound so much. I didn't like the Millet at all, thick and syrupy. The Raptor was a fun amp too, with a completely different signature.
I would like to be able to get into tube amps, but it's a whole new playing field when you make the switch. Tube rolling, source synergy, and headphone synergy all make it a very expensive switch.
The Eddie Current EC/SS is lovely. Powerful bottom, thick mids, a bit warm on the upper mids, yet the treble comes back and extends to the stars.
Maple Tree HD+ Purist seems to be the most recommended tube amp for RS-1's. I would start looking there.
The RS-1's, I took a few good listening periods, and used it to realize my ears would not be kind to me if I kept listening.