I inherited an old Mac Mini...It's a 2.4 Core 2 Duo model with, I think, 4GB of RAM. Right now it has Snow Leopard on it. I'm planning on using it as a mainly a file server and possibly light web machine...not much more. What would be the best OS to update it to? I'd like to get it as current as possible without sacrificing speed. Eventually I may drop in a cheap SSD and add some RAM. Thoughts?