2k? ... I'd have to say...
Cervelo P2sl ultegra - $1650
Disc Cover - $100
Aero Helmet - $125
Visiontech aero basebar - $75
or...
Argon 18 Mercury $1300
Shimano 105 build kit $600
Disc Cover $100
Aero Helmet $100
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Should be equally fast. Obviously the Cervelo has more bang for the buck. The Argon 18 is a little more unique.