Fast:
700c tires, triple chainrings, 7-8 gears out back
Smooth:
70X35-38 tires
retro-looking:
down tube shifters or bar end shifters
polished aluminum components
super wide centerpull or side pull brakes
Comfy:
get the bars high up and get one that fits.
That's how I'd build up a fast, comfy, retro, smooth Cross Check.