I tend into the fall further into the 'well designed digital amps played within their clear power limits sound the same' camp. This is based solely on a lot of written research I have done. The arguments for equality always seem to provide scientific notation and controlled test results while the arguments against always seem to be based on opinions made without a proper test environment. That being said, I'm always willing to keep a very hesitant but slightly open mind and I would love to participate in such a test.
However, I did want to mention that certainly I do believe you when you say you can hear differences between tube amps and digital amps. Obviously this is not an apples to oranges comparison. My newly learned knowledge and even newer experiences say that tubes, by nature, add a mild level of distortion that is often considered pleasurable to many ears.
Also, it is my understanding and my listening experience that swapping various types of tubes can produce slightly different effects on this distortion thus changing the sound or more descriptively, "the warmth" that tube owners have come to love over the years.
I think I've become a bit of a purist in that I want to believe that what I am hearing is absolutely as close to the original, real life sound. At least as much as is possible within my financial limits and the within limits of my sensibilities (law of diminishing returns.)
However,
after spending a fun evening with a gentleman with a gorgeous open tube amp setup where it was very easy to change tubes (and he had a lot), I have to say that someday when I have cash to spare, I'd like to invest in a nice tube amp for a change of pace now and then. Especially one with big, in your face, VU meters!!!
