Reading through this thread, I can see where Rob is coming from. Myself, I'm in the same camp as Weas, and prefer non-master volume amps. I still have a couple of master volume amps, and sometimes use them.
If I was playing metal, or some of the session gigs that Rob does, I would probably rethink my equipment. I can see why he's looking for the next thing that's going to rock his socks off. Since I am playing in a hard rock/stoner band that bases it's sound more in the line of the Groundhogs, Pretty Things, and Iron Butterfly than most of the stoner bands who are more in the Sabbath camp, I am looking for a more open or clear sound, mixed with a more acid '60s vibe. That's why I prefer Hiwatt and Vox, but also like non-master Marshalls. I have to with the sounds created by the base player. I would never cut trough otherwise. Between him and the drummer, there is a heavy wall of sound I need to get through. My other band is an Alice Cooper cover band basing it's sound of the original '60s to early '70s line up. Again, very primitive and only needing one pedal. I know my place in the sonic landscape of that band, and what my role is.
Since I look for sounds that work for the whole picture, I am painting with a certain palette that others wouldn't. Just as Rob is hunting for something that he presumably wants to take him over the top. Tone is very subjective as mentioned before, and one person's needs are rarely the same as another's. I am painting for my own personal abilities, strengths, disadvantages, song writing, and overall sound of three people playing in unison.
That being said, I know that if I plug any of my guitars (Gibson, Rickenbacker, Fender, homemade) into any of my amps (DST, Fender, Hiwatt, Marshall) I am going to sound like me. If I spent the money on a Trainwreck or other high, high end amp, I would probably still have my own sound and wonder if it was really worth it. I've known a couple of good builders of Trainwreck clones, and I would really love an Express. I just don't know if it's really the right amp for me when I know what already works for me. And Trainwrecks do need to be played loud to work properly. Also, since I am not really a professional musician, I also need to know when to say "enough." Because I am running out of space in my house, I am just about at that point. I should be more concerned with playing than accumulating anyway.