I think you'll be fine with the tri bike if that's the route you take. I believe Cervelo stopped making the One this year, but several people on trifuel have recommended the Dual. You can read reviews on it here:
http://gear.trifuel.com/review.cgi?ID=418
I've also had several people recommend the Giant OCR series road bike that they converted to tri specific and as well the Kestrels.