I think proper etiquette might be to create just one thread for this, instead of starting a new one for every bike you consider.

In that price range, you really can't go wrong with any particular one. Trek, Specialized, Cervelo, Kestrel, Felt and others all have an entry in that range, and they're all good. Which one is the best for you will depend on which one you like riding the best.

That looks like a good deal on the Kestrel, to me, but I believe it's a fairly aggressive geometry, which may be uncomfortable to you as a beginner. No one but you can make that call, though, as you're the one who has to sit on it for five hours at a time.