I've just installed a Corsair H50-1 CPU cooler which is great for keeping the CPU cool but also means there is no airflow around the CPU anymore for keeping the northbridge heatsinks cool
Just use this Zalman fan bracket to hang a quiet fan over the CPU area. Voila! Instant air flow. I've used these before and they are quite sturdy.
(Apologies to Best Byte for hotlinking photos, but I'm also linking to product page so maybe they'll get something out of it in return. I've ordered from them before and they're legit. Disclaimer: I have no connection with Best Byte other than twice being a satisfied customer.)