Hate to say it but Fast comfortable and light does point to C.F.- unless you have more money.
Top end aluminium frames can meet all of your criteria- but they are fast being run down by the shops. C.F. is the new product but Even the stiffest aluminium frame can be improved with C.F. Forks and seat stem.
Then there is the manufacturer. Going through just one that I know-Giant- and there are several models that will fit into what you want. Trek will have the same- so will Specialised and Bianchi and Cannondale and---(just add your favourite manufacturer here).
The bike is not the problem but the dealer is. You have to find the right LBS.
Two bikes seem to stand out that 50+ers have been happy with. Specialised Roubaix in all its different forms and Giant TCR C and SCR C. And I know I have a TCR C so it is a plug for my bike- but I also have Boreas and that is my bike of choice.
Edit- Aluminium with C.F.Seat stays- Look at the Giant TCR-Alliance A1. Well worth a test ride.
http://www.giant-bicycles.com/en-US/...ad/1237/29254/
http://www.specialized.com/bc/SBCBkModel.jsp?spid=34081
http://www.trekbikes.com/us/en/bikes/road/