Tried one (twice) in my search for a tubier version of my LMIII, and thought it was indeed very very subtle. Given that I was looking for some warm breakup and even more towards drive, I may have needed more than you did, but it wasn't enough of a difference for me to change from my LMIII. The LM Rocker, by contrast, was just about as subtle as a brick - at about 15% of the tube dial it started to fizz, and stayed fizzy the rest of the way round. I found the RH450 the best tube-sounding head out there, so I bought one.
I'd really, really try to try before you buy, though - your ears are everything. If you're anywhere Bass Direct (Warwick-way, and even if you're not, it's worth a day out), Mark has a great selection of mini-heads, including the MB, Genz and TC ones.
Edit: Just read the above comment, and I did have a Sansamp BDDI in front of my LMIII for a good while, which gave me the Ampeg-y tone I was after. I can get this from the RH450 on its own, so I sold the LMIII and the Sansamp. The Sansamp isn't exactly subtle, though. If you can't get to a shop to try, if I was you I'd consider buying a Behringer BDDI box for £30 or so, because this'll give you a ballpark of what the Sansamp sounds like.