A Phenom II... I wouldn't remove the IHS from that IMO. If I remember correctly, the PII's had the IHS soldered on. Removing an IHS that's soldered doesn't really make too much sense, seeing how the solder isn't going to dry up and go bad like the old TIM used too.
If you want to get slightly better cooling, I would recommend lapping the IHS instead of removing it. Lapping is much much easier than removing a soldered IHS. You can still kill the chip if your not careful, but its way less risky