Study of Athlon 64 Overclocking Techniques - To summarize,
memory dividers are a perfectly acceptable way of maximizing system performance, as CPU clock is the factor around which everything revolves, HT link speed is not of great importance (even 600 MHz ought to be enough for 99% of users), and the absolute best way to squeeze performance out of your K8 system is to avoid the use of a memory divider, though that requires high-end memory.