Yea the I7's run quite hot and well the stock heat-sinks will keep them from burning themselves up it doesn't really do much more then that. You can try re applying the thermal compound and see what that does sometimes it will loose its effectiveness over time depending on how old it is. For the little bit of load that you are putting on it and for the temps to jump up to 70 that easily tells me that that heat-sink simply is not doing its job so take it off make sure it has no dust clogging the fins re apply some good thermal compound and see where that gets you.
Now you dont have to spend a crazy amount on a heat-sink to get some good temps you can get really decent heat-sinks in the $40 to $50 range that will help get those temps down.
XIGMATEK Intel Core i7 compatible Dark Knight $44http://www.newegg.com/Product/Product.aspx?Item=N82E16835233029
This is a great heatsink and is sure to get those temps down just make sure your case can fit it.
Before you go out and get a heat-sink definitely try new thermal compound first see what happens.