Its probaly better to buy a more powerful fan like a 420m3/hour, even if you don't need it at full power, you can dial it down with a fan speed controller and if you ever decide to uprgrade to a 1000w you don't have to upgrade your equiptment, its also less noisy. Also, buy here www.growell.co.uk, best prices I've seen. Personally I would buy an air cooled reflector but its really your decision to make, I'm still investigating the best possible option.

http://boards.cannabis.com/showthread.php?t=76954

Hope this helps. Let me know what you end up doing.