At least a 54" if not 60". I'll be getting the 48" rangetop with griddle and installing a 60" dual extractor fan wall hood. Proline hoods are comparitively cheaper and seem just as effective and cheaper than Wolf which is also under comsideration.

54" if you can fit it. The range is deeper than normal too so you really want a 27" deep hood if possible.

I have a 48" hood insert over my pro grand steam. I didn't want the hood to be an enormous focal point. Has done the job quite well for the last 2 years.