Your first road bike will likely be the one you stick with for a few years, it's worth the investment if you ask me. First; however, I would consider not spending the entire budget on the bike. Frankly, $2500 is a solid sweetspot for the bike, this would leave you with $1000 left over for power meter, smart trainer, kit (you can easily end up spending $500 for a wardrobe of Ralpha or Castelli)—Helmet, Road Shoes, Garmin (or Wahoo) GPS device, a bike fit (easily $200 right there), etc.

IMO, shoot for a Carbon frame from a reputable manufacturer, make sure it has some nice wheels (deep section carbon IS FAST), DI2 or E-tap is AWESOME, but not a necessity, and disc brakes would be very nice.