If you're not overclocking, why do you need better cooling in the first place? The A64s run pretty cool even with stock cooling and if you want to prolong the life of you chip you can enable Cool N' Quiet and download the AMD processor drivers that will turn down the voltage and clock speed on youor A64 when it is idle so it will run cooler. Even if you are running DC projects 24/7, the stock fan ought to keep the A64 well with its thermal limits.
I really think people can get a bit too obsessed with processor temps on this forum ("OMG, my Prescott is 70C!"). As long as the system is stable, then I wouldn't worry about your processor temps. Just use the stock HSF until the fan dies or gets too noisy to live with, then replace it. By then you'll probably be upgrading the processor or even the whole rig anyway.