Acutally, if you really want it to fly, get an SSD for the internal drive and then a 1TB external to hook up to it for storage purposes. The SSD will make your files (and OS) load much much faster.
you could get external hard drives the length of your palm if not shorter, and way thinner. all you need is a short usb cable. if you travel a lot you could easily put them both in the same bag you keep your laptop in. it will reduce clutter on your actual computer and increase operation speed considerably.