I have around 300gb of music but I haven't listened all of them either, they are there for me to listen to. Whatever my mood demands, I find something in the folder.
I would like to have them with me all the time too, but I know for the moment it is quite a dream. So as much as possible is a reasonable wish. I think 128 gb and over is good enough for the moment.
Btw, Mim, did you preorder NX1 ZX1 (sorry, a letter mistake)? I see it at pricejapan.com too, the price is not so high than X5, maybe I can wait a little longer, save a bit more and go for it. Sony is an old friend from my childhood, if they want to return to audiophile world again, they are more than welcome.