Interestingly we (also a Raspberry Pi Approved Reseller) tested these heatsink cases with fans attached and found that the fans didn't improve thermals due to t

Interestingly we (also a Raspberry Pi Approved Reseller) tested these heatsink cases with fans attached and found that the fans didn't improve thermals due to the manner in which they are mounted. In the end we decided the extra cost, power consumption, noise, and moving parts simply weren't good value for the customer! Adding fans could (and should) make a huge difference but this specific design was very poor at taking advantage of them.