I would go with 100 and turn it down to the right level with a lamp dimmer. Make sure that you get a quality lamp dome since the heat emitters get really hot.

I would suggest one of these:

http://www.zoomed.com/db/products/En...lnaHRpbmciO30=

http://www.zoomed.com/db/products/En...lnaHRpbmciO30=