Hello Mike,
what I was trying to say, was "Why do you want to get 100% cache hit ratio ? Is there right now any performance impact you see ?". - You will always have situation where data isn't in the cache and needs to be read from disks (for example a year / quarter end report).
From my experience a page size (for you 16K) and an extent size pool (128K in your case) is enough. Seperate the log into its own cache and check if you have 'hot tables' - for these tables a new named cache makes sense.
A very good resource to improve the data handling can be found here:
http://www.sybase.com/files/White_Papers/Managing-DBMS-Workloads-v1.0-WP.pdf
It will help you to find the bottlenecks. You don't have to use trial and error, but you need to verify what changes would make sense. Caches are only one way that could help you to avoid performance problems (IO tuning, query tuning etc. are other thinks you should check).
I hope this will help.
With kind regards
Stefan