If you do a good job of cleaning up both your core and your hs then AS2 would do wonders. Otherwise, you prolly shouldn't bother.
I think AS is amazing. My old K6-2 450 has hit new record speeds with my Coolermaster SocketA cooler w/ ASone. ATM i'm running at 495Mhz, I can EASILY hit 517Mhz, but my psu is low rated and I get random resets due to power fluctuations.
AS is very competitively priced, especially considering it yields thermal transfer rates 10x higher than generic paste. I remember some statistics that radio shack paste is something like 1.05K transfer while AS2 is 5.12K transfer.