Recently I've been really frustrated with my iPhoto/iTunes performance where all those libraries are stored locally in my iMac (5400rpm harddrive). The size of those two libraries combined is roughly 300Gb. I'm trying to decide if it will be worthwhile purchasing a big SSD external drive. Will I see much gain? Will the external connection speed limit the speed of my SSD drive anyway? (Because I can't upgrade my iMac's drive internally). Thoughts?