You probably know what I'm going to say. Steel. Bike.
Steel is one smooth ride. Check out - Surly LHT, Surly Pacer, Surly Cross Check, Trek 520, Jamis Aurora, Jamis Quest, Jamis Satellite, Jamis Eclipse, Raleigh Clubman, Raleigh Sojourn, Specialized Allez Steel Double, etc, etc. Or any steel framed bike. (Maybe a used Mixte if you're into those.) A touring bike would have a less aggressive posture. Jamis Auroras have an adjustable height stem. So you can ride more upright if you like. Well, I wish you luck. 
(You could always upgrade any of these to your specs.)
"Things look different from the seat of a bike carrying a sleeping bag with a cold beer tucked inside." ~Jim Malusa
2009 Trek 520-Brooks B-17 Special in Antique Brown
2010 Surly Long Haul Trucker-Brooks B-17 Standard in Black
1983 Fuji Espree Single Speed-Brooks B17 British Racing Green