I've gone through much the same - and I'm just now getting ready to revisit the game.
I'm a tenor player.
My closest approximation of an acceptable alto tone was on a Super 20 that made an unfortunate trip to the repair shop. Next closest was a Selmer Serie II but I let that one get away to a friend that craved it more than me. Now, years later, I am getting yet another II. I found my best mouthpieces were the SR Tech L85 and a Jon Van Wie refaced Meyer 6MM opened to .080. I'm currently questing again for mouthpieces. I'll see whether Fred Lamberson has any alto mouthpieces coming up soon. In the meantime, I'm looking for another L85 and talking with Ed Zentera about another Meyer - this time I'll go a little bigger in tip opening and a little smaller in chamber size.
I'm with ya tho', Chi', once you start filling the room with tenor tone, you want to hear MORE from the alto. I don't know that it's beef, maybe it's just a large bowl of Ben and Jerry's "Chunky Monkey" or "Double Chocolate Fudge Brownie" or somethin'.
Check in when you find something that works. Maybe it's just learning to blow through the horn like a tenor that makes it fill the room. I've a friend whose Serie II alto sounds huge with a RPC .095 (red letter). I just don't think I could harness that setup. The guy has been playing alto for most of 60 years and that's a tough combination to challenge. Hmmm, funny. When I hear him on tenor (a Yamaha 61, I believe), I think "His alto sound is so much bigger, I wish he'd stick to that."