Hard to beat a canyon ultimate 8.0, rim brakes, full ultegra on a carbon frame for $2500 and it actually comes with good Conti tires as stock so you don't have to buy new tires right away. That being said, it's not the most aero thing in the world (but can you really get a new aero bike under 2500 anyway?) And this canyon has the one piece stem/bar that would be hard to mount aero bars to. If you downgrade to the 105 version it's only 1800 bucks and has a normal handlebar which would be easier to add aero bars to. As with any direct sales place it takes a little more knowledge to get the right size, but it's a heck of a lot of bike for the money.
Something like a 105 aluminum bike and some deep carbon wheels could be a good plan too, like an specialized allezelite with lightbicycle brand carbon wheels
Plenty of budget to get a nice bike at 2500!