I have a David Kirk. He was great to work with and I got a fantastic bike. I don't think you can go wrong here.
Maybe consider tubeless instead of sew-ups? I love my tubular wheel set, but these days they only come out for special appearances and re-gluing tires really is a PIA.
You didn't mention rims, but if you want deep carbon rims now or in the future then disk brakes is probably the way to go because it gives you more options for wheel shape and less worry if you have the correct brake pads, how much heating is happening down hill, blah blah.
Also disk brakes allow to go faster bombing down hill than rim brakes because you brake later before turns.