Can I ask you what you prefer about solid-state? I've been looking towards valve amplification in my desire to sample the "next level" but most options involve importation and I'd prefer to give Wastemonster as little of my money as possible. There's also the inherent fragility of valves to consider.
Can a solid-state amp be a real step-up from my O2? What would you recommend and, if you don't mind, why?
Sure, that's not a problem at all!
At the recent meet I got a chance to try a few tube amps ranging from the WA7 Fireflies amp to a DIY ($500+) 'shoebox' amp. I didn't get to make any hard comparisons between a lot of them, but the two mentioned definitely have that signature 'tube' (I.e. warm). Both were very wonderful to listen to as well.
However, I listen to a lot of very fast paced, busy, and frequently heavy music. While I had the HD600, with the Asgard 2, the sound good get a but fatiguing at times, and would just be too bright. I even gave it a shot with my GoVibe Magnum amp/DAC and I came off with similar results.
However, I decided not to give up on Sennheiser and give the HD650 a shot. I was skeptical, but I'm glad I did it. I got everything I was looking for the HD600 to be for me. A more relaxed sound in the treble/highs region, and a better extension in the bass/lows region.
Now getting to try the HD600 on a tube amp, along with the AKG K701 and K812 was a treat. It really fit their sound IMO. However, because of my taste in music, and my desire in the sound, I just prefer the 'solid-state+sound'.
I might have missed a couple points, but I'm on a lunch break. I'll reread it when I get home and feel free to ask me anything if I didn't make a lot of sense .