What is your noise tolerance like?
I try to get the fan with the highest airflow and highest static pressure that stays below about 40dBa. Sunon has an 80mm fan that delivers 50.6CFM at around 40dBa noise.
I'm pretty sure you can mount a 92mm fan on the SLK900, so you can probably find a fan with better airflow at no higher a noise level.
I like Papst, Panaflow, and Sunon brands.
www.1coolpc.com stocks the 80mm Sunon I mentioned above... they may also have a similar 92mm fan.