i have some recent experience with this topic and some odd observations. i began, as you, ripping and storing on my laptop and about 6 weeks ago had filled it. this led to the process of evaluating external storage...nas, usb hd etc and i finally decided an a seagate blackarmor nas 110. i transfered all my music from the laptop on to the nas and to my big surprise, i had a noticeable improvement. things were airy and open where as i had a muddy, loose sound with my laptop (this negative change in sonics occurred as it got closer to full, was not always like this). very strange but very real. my guess is this had to do with overload on the processor in my laptop as there were more than a few quirks with the drive full. i realize many will say i am crazy but that is what happened. i am finding more and more that everything matters in computer audio. stuff we used to think did not actually does. i have a feeling we will all learn allot as this format begins to mature.
good luck with your transition...
good luck with your transition...