I looked at the Cannondale CAAD 8 with Sora, their entry model this morning. I was amazed how nice the bicycles at that level are now. The wheels are probably the "weak" point but that is how things seem now to us. Several years ago this would have been a first tier bicycle. I'd suggest the Synapse, as suggested above, in either aluminum or carbon fiber, at the 105 or Rival level if you want to try a Cannondale. Your Roubaix was one of the nicest riding bicycles on the market.

The Specialized Allez, Giant's and Trek's entry level bicycles are all super. Your budget will get you somewhat above entry level.

Best of luck in choosing.

Bill