That is a pretty high idle temp for an AMD CPU. I have never used one, but have heard that Asetek makes some fairly good coolers. I believe they make the Corsair Hydro series coolers. I would suggest following some of the advice given above and completely clean the CPU and heatsink of old paste and re apply a good quality paste in a proper manner. If that does not solve your problem, I would consider a better cooler or air flow set up in the case. And as has been said above, liquid or air need the same thermal paste, it makes no difference.