The hard drive options for the computer I selected are:

500GB 7200 RPM SATA Hard Drive [Included in Price]
640GB 5400 RPM SATA Hard Drive [Add $35.00]
128GB Solid State Drive [Add $154.00]
256GB Solid State Drive [Add $445.00]

They all seem to be equal but the amount of storage.
I would do the 640GB 5400 RPM SATA Hard Drive its not that much difference so why not and i like to listen to music and like I said before watch movies so that will be enough for me.