SSD drupal performance improvement
I am managing a site that gets about 1000 unique visitors a day. Not sure how big your application is, but 1000 is enough to cripple a default drupal install.

I added the standard performance optizations, apc, etc, but found that memcache by far had the best result. My pages used to take 20 seconds to load. Now pages load instantaneously. If you have not tried that, I would see if that helped first before investing in the SSDs.