Your hd's wont like such high case temps one bit, they usually get problems at 55-60 and normally they're quite a bit above case temp (my Barracuda IV was 44c at a case temp of 32C when I checked quite a while ago and Barracudas are cool running). IBM has directly stated that 60+C (internal temp not case) is deadly for their drives.
You can get 12db case fans, 80mm at least, they're very silent, you won't notice them but even though they do not move that much air it should help tremendously.