If you're even asking, get a cross frameset. But build it up like a road bike.
There's a big range of cross frames out there to match all but the very lightest and raciest road frames. It's just a matter of your budget and what is important to you.
Depending on your tastes, you might want to use Tektro Mini-V brakes instead of cantilevers. They work with short-pull (road) levers, don't need cable hangers, and some people prefer their performance.
