Regarding SQL Server, SANS and SSD's: just a couple of years ago we had a middling SAN which ultimately couldn't cut it performance-wise. Actually it was awful, but that was mostly due to the fact it was asked to do more then it was designed to do. What we are doing now is spending a lot of money on a new SAN at our new data center (leased) with tiered storage (SSD's being Tier 1 for example) with priority access to that tier given on a system by system basis at the database server level. It's been a beautiful thing. Initially we had a pretty small SSD pool, for 2013 we are spending many tens of thousands of dollars on them.