Most people like CX bikes as a jack of all trades. The Soma Double Cross DC is supposed to have a disc brake option. However doing a quick glance at some of the brands it doesn't look like many have them though I am sure there must be others.

What is affordable though is really relative on what you are willing to spend.

A list of bikes within a relative price range that might fit your purposes are the Surly LHT and CC, Specialized Tricross, Bianchi Volpe, Trek 520, Cannondale T2, Jamis Aurora, etc.