advice on new exaust fan

hi im upgrading my shitty little bathroom extractor fan i have in my grow room(walk in cupboard). i use a 400w hps light and my temps a little high 85-90. i have seen this fan on amazon http://www.amazon.co.uk/gp/product/B004BRO9PK/ref=noref?ie=UTF8&s=outdoors&psc=1 i was just wondering how loud 46 db is ? would this fan do the job im after or should i spend more on a better quality fan is basically my question.

no way around it, the more CFM the louder the fan.

I have had good experience with these fans for room exhaust.

http://www.google.com/products/catalog?q=hydrofarm+inline+fan&oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&um=1&ie=UTF-8&cid=15392996312738790407&ei=TXcjTfzMBoj2tgPwuu2ZCg&sa=X&oi=product_catalog_result&ct=result&resnum=5&ved=0CDgQ8wIwBA#

either the 8 or the 10. they are not "quiet" but they are not too loud either.

Well i bought this 6"rvk style fan http://www.amazon.co.uk/gp/product/B...outdoors&psc=1 and i must say for the price its superb. Dropped my temps to 77-78 with my door closed and the fans not as loud as i thought it would be. Hopefully thats all my heat stress issues over