Well, the case certainly wont help, but thats still stoopidly high...
AS3 is very old, try some Arctic Cooling MX-2... I just got some and it's fantastic, easiest paste to work with i've used and much better than AS3 or even AS5 for that matter... I would guess applied correctly that it should give you approx 5-6 deg temp drop...
Lapping the CPU will give you an extra 2-8deg to play with depending on how bad the IHS is to start with. If you dont want to lap it yourself there are plenty of places that'll do it for you, but TBH it's easy enough to do.