Road bike- upright geometry or more aggressive?

Ok, this is a "which bike" question but my situation may be relevant for a lot of newer folks.

This will be my second year of tri's (2 sprints +1 olympic last year and at least 2 sprints + 2 olympics this summer+ possibly a HIM).  I will also do the weekly club rides and a century or two.  I might get spunky and try the local crit.  Bought a used Trek 1200 to get started last year but the frame is on the small side.  I ride with clip-on aerobars.

I will spend approx $2K.  The two LBS's I like carry Cannondale, Scott, Giant, and Trek. 

Should I go with a more upright bike like a Cannondale Synapse or the new Giant Defy Advanced?  Or should I go a bit more aggressive like the Scott CR1 or Cannondale Carbon Six?  The more upright geometries probably make sense but I've never had a problem with getting down, even in my aerobars on a bike that's too small for me.  What about tri's?  I've test ridden a few but it's hard to tell in the parking lot.

Thoughts?  Experiences?