Generally, cache on HDDs is considered fairly unimportant. I remember reading an article a while back about cache and how Western Digital saw no significant performance difference in going from 32MB to 64MB cache, but ended up going to 64 simply due to its competitors also making the transition. Having at least some can increase system smoothness, but, really, having more memory, utilizing SuperFetch (which is on by default in Win7/Vista), or running a RAMDisk or flash drive as a ReadyBoost cache would likely make a vastly significant difference over going from 16MB to 32MB of HDD cache.