actually i'd still suggest the freezer 64. its one of the best overclocking heatsinks out there... maybe you just didn't apply it right...
what temps are you getting (idle and full load), and how far did you overclock it?
i think what would be better, rather than a new heatsink, is a nice fine shiny finish on that heatsinks cpu surface... just lap the bottom of the heatsink with some low grit and work your way up to mirrored finish sandpaper.... it really helps a lot.
the best heatsink on the market in my opinion is the thermaltake big typhoon, though it can take up a lot of room in the case... and it can be tough to apply.
if you're serious about it, i suggest that you don't bother with a new heatsink, and lap the bottom of your current one down to a mirrored finish... then you can buy some coolabs liquid pro thermal liquid. its like 10 times better than arctic silver 5, but if you don't know a whole lot about it then arctic silver 5 is much safer and still a really good compound to use. coolabs liquid pro is dangerous because it can have a nasty reaction with aluminum... so you'd have to be extremely careful with it.
http://www.overclock.net/faqs/15897-info-want-lap-your-p4s-a64s.html
very good guide, with pictures ^
note, the smoother the surface, the less thermal compound you will need! put too much thermal compound on, and you may as well have not gone through the trouble of lapping it at all! good luck!
what i did was i went to autozone and they had 320-2000 grit types of sandpaper, took a piece of glass out of a picture frame, and used a paper towel (folded a few times) to cushion the cpu pins and about a half hour later i could see my face in the cpu integrated heatsink (ihs) and in the bottom of the heatsink. i lost probably 5-10C with this mod... its worth it... also note that if you lap the cpu heatsink, it voids any warranty on it... so careful with that FX-60 of yours!