your temps are right about on target, perhaps a little warm... but then again if your room temp is 25*c then that is to be expected! At my home we are typically at ~20*c, so my idle is ~25*c (5* delta), and 4.2GHz load temp is ~65*c (45* delta). You have a 5* idle delta, and a 35* load delta, so you have plenty of room to OC with.
If you want a little better cooling performance, the fans are easy to replace. On mine I have 2 corsair quiet 120mm fans as a push-pull, and that helped a bit, but I did it more for the noise aspect than cooling. Better thermal paste will bring the temp down 2-5*c under load, but I would not bother with it unless you really are in need of dropping temps, and you are fine where you are at.
So long as your...