imo the best thing to do is probably try to get them into 4u servers so you can run 120mm fans and taller coolers.
the smaller cases use the smaller fans that spin higher rpms to move the same amount of air.
im with linkenparkfan007. but just use the modem the isp provides you and get a separate router to do everything. that's what im doing. also don't get the wndr3500 step up to the wndr3700 as it owns the other.