Solo Rider, always DFL
Join Date: Jun 2006
Location: Beacon, NY
Bikes: Cannondale T800, Schwinn Voyageur
Don't think you would need a new chain, new wheels, a new saddle or new brakes... MTBs usually have pretty powerful braking, why do any swapping of that?
Tires definitely will make a difference, and a set of bars with more positions would be helpful. A narrower range "road" cassette would probably make it easier to get a happy cadence all over the board (plus mountain cassettes have a low gear that are mostly not useful on the road.)
If you like the saddle you have now, don't switch that either... it takes most folks hundreds of dollars and a world of painful rides to figure out what works and what doesn't. Why do you feel like switching that out??