So my iMac is very slow, which is to be expected for a 7 year old computer, and after looking at various threads about how to speed it up I'm thinking my best option is to replace the original HD with a SSD. So I would like recommendations on a SSD to put in there. I'm in college so I don't have a lot of spare money, so I'm thinking a smaller SSD for the OS and apps, and then using an external drive for any large storage needs.