Thermal pad or Thermal paste?

hey there,

after some excessive amount of case modding to fit 4 additional
suckholes/blowholes (3 in the side case blowing IN and 1 on top of case
blowing OUT), i've finally managed to bring my case temperatures under
control -- about 6C above the room ambient (ambient is 28C, case is 34C).
But my case to cpu temperature delta has gone out of whack! previously with
my case open and a floor fan blowing into the case, the cpu temperatures
hovered about 18C above the case/system (when idle), but now it's a shocking
24-25C above the case temperature (currently 58-59C when idle). Thus I've
decided to chuck the retail AMD HSF and get myself a Thermalright SLK700
cooler.

Now that the backgrounder is done with, my actual question: should i use
thermal paste instead of a thermal pad with my new cooler? I've read that
AMD will void your CPU warranty if you use thermal paste/grease. Also would
thermal paste require any maintenance, like removing, cleaning and reseating
the cooler every few weeks?

thanks,
vin