Caframo Bora is what I used in my last Westy - after being seriously
disappointed in the Hella fan build quality (China - so poor I returned
them). These Caframo fans, while not cheap, are very quiet and draw only 1/4
amp on high. Made in Canada. I found some in black when I originally bought
mine.
http://www.ebay.com/itm/Caframo-Bora-Marine-Fan-6-3-Speed-White-/190731340035?pt=LH_DefaultDomain_0&hash=item2c68794903

For more ventilation I use Fan-Tastic Fan's Endless Breeze. Sets up nicely
on a cabinet and I've often hung it on bungees in the front screen window of
the canvas on hot nights. Also very miserly on power and very quiet.
http://www.pplmotorhomes.com/parts/rv-converters/12-volt-fans.htm

Karl
www.westyventures.com