Rich, for a triathlon/time trial bike, I would recommend a model with an aluminum frame, Shimano Ultegra, Sram Rival components or Campagnolo Chorus (these provide maximal value for the performance), although I wouldn't reject a Shimano 105 bike. Either 9 or 10 speed (I prefer 9 speed of the additional cost of 10 speed). Orbea, Trek, Cannondale, pretty much all the major manufacturers offer packages like this. The Orbea Ora is nice. I don't think you need carbon fiber at this time, but if you come upon a great deal with carbon fiber - go for it.
As for wheels, eventually you'll want to get some carbon fiber wheels and maybe a sold disc, but that is an entirely different discussion.