New grease is a very good idea instead of the stock pad that is on the bottom of many heatsinks. If you don't use grease you are going to have big problems. 66C is to hot for the cpu.
You system is running way to hot. The 40C system temp tells me you have no case cooling installed. What size case do you have and are there any case fans in it? Try running with the sides off the case and see if that lowers the temps.
Still to dang hot. What HSF and fan are you using? Try a WBK38 or a FOP32. Also put some good case fans in. Make sue u take in as much air as you take out. This will probably get you down to the 40's or 30's.
is that temp at idle or full load???
if it`s at idle then it is way too hot still....
try making a duct to the fan to the side of the case so that it will get some cooler air to the HS.
u can make them out of card boards.
You still never told us what H/F you are using! That could be part of the prob to. There are a lot of new H/F out there now but 2 that I recomend depending on how much you want to spend are GW Fop38, this is very good and cheap to and if you can't stand the noise of the delta fan you can always replace it with a 80mm fan later on. If you have money to spend it is hard to beat Swiftech.
That sounds better, but one question, what voltage settings do you use?
The case temp is still very high, and you should get some good case fans..
I would recommend something like 120mm in Front and 2x80 mm in the Back. Front blowing in, Back sucking out.
If the 120 mm doesn´t fit, 2x 80 mm in the Front will also be fine, but a bit louder..