You will be faster on a $1700 aluminum-framed bike with an aero helmet and race wheels than a $3000 carbon bike with a regular helmet and training wheels.

I'd suggest you look at bikes in a slightly lower price range, leaving yourself room to upgrade to some nicer wheels and an aero helmet.

Test rides tend not to be as helpful for tri bikes as for other bikes. There are simply too many points of customization to get a good idea of how the bike will feel, such as tire type and pressure, saddle type and aerobar choice.

Learn what kind of tri bike best suits your body type. The stack/reach articles, combined with the stack/reach database of bikes over on Slowtwitch are a great resource for that. Then, see which bike shops in your area sell bikes that would fit you and begin shopping!