Cool! The 610 will definitely be easier to convert down to 700c, if those current brakes don't have the reach just throw some Tektro R559s on it. However, there is nothing wrong with 27" wheels. If you wanna get really fancy, keep the rims, and get new hubs and spokes and have someone build them up for you, if you can't do it yourself. I've thought about doing it to a bike I converted down, I just haven't wanted to spend the money. That way, you can put a modern cassette and drivetrain on with no problems or worries about brake reach.