How to setup large database access/cache on LAMP environment?
50K rows tables are rather small. Before throwing more hardware at it, I'd recommend checking/tuning the following:


my.cnf setting: make sure you have good buffers on InnoDB buffer, Key Cache, Query cache, etc. If website is calling same queries over and over, query cache could help.
Check slow query log and optimize worst queries. It'd say this would result in best result for your efforts.


You may need to normalize some tables, but above two are least invasive options that could take your DB performance to next level.