Hi, Looking to upgrade my 21.5" i7 mid-2011 iMac from 4 GB of memory to 8 GB, at first I was thinking of getting an 8 GB kit and then I'd have 12, but I figure that would probably be overkill. On Crucial I've found this 4 GB kit for £32.39, theres also an actual 4 GB module, it's more expensive but there isn't any performance increase is there? Although that is quite cheap, is there any places I can get this cheaper? Thanks. EDIT: I found this, will two of these be okay? Works out cheaper.