Don't rule aluminum out completely. Some of the higher end aluminum bikes, such as the Cannondale Synapse, are noted for having a very nice ride quality. If you want disc brakes you may be pretty much limited to steel or aluminum. It's also possible to get aluminum with a carbon fork, which goes a long way to smoothing out road shock. Then too, if you can put slightly wider tires on it (say, 28c instead of 25c), that also helps with cracked and broken pavement.
http://www.cannondale.com/can_en/201...n-s-disc-5-105
http://www.giant-bicycles.com/en-ca/...1/20446/79986/
If money is no object, there's always titanium:
https://www.lynskeyperformance.com/s...ance-bike.html