Cannondale Slice 5/Cervelo P3.

I woul dbuy the frameset, plus the bars and seat, and convert to Single speed via spacers and tensioner, or convert to fixed via. Eccentric rear Hub.
If the frame goes over the budget, I would prolly just grab myself a Leader frame.

But the P3s from Cervelo are also nice.

Id throw in a front White Deep V and a white disc wheel at rear.