I saw your query about this on the Surly LHT/CC mailing list. I think steel is going to be more comfortable for you than aluminum. If a LHT doesn't suit, why not something like a Gunnar Sport? It's a more relaxed geometry with the comfort advantages of steel.

I'll second (third) the Salsa recommendation and add Soma to the list of bikes to look at. The Smoothie might suit in the same way the Gunnar does. It may be hard to find a built up Soma or Gunnar, so that may dissuade you a bit.

You could certainly also look at a carbon bike. It's not going to do a rack very well, but with an alloy seatpost, you could use a seatpost mounted rack. Here again, I might go with a more relaxed geometry bike like a Roubaix, a Pilot, or a Synapse.

Good luck!