For the basic external drive I'd go with a Western Digital 'Passport' drive. I still have less trouble with their drives than any other brand but as with anything, you might be unlucky and get a duff one. Something like this -
http://www.amazon.co.uk/Passport-Ult...l+2tb+passport .
As for NAS box, I tend to advocate buying a disk-less NAS and fitting your own choice of drives rather than buying a complete 'off-the-shelf' setup. For the drives to use, grab a pair of Western Digital 'RED' 2TB as these are designed for use in home/small business NAS units. For the NAS itself, it's all down to what you want to use it for. For simple storage only, I've had no bother at all with Netgear ReadyNAS 102 units. If you're going to use it as a media player, there are better units out there, including some that connect directly to the TV via HDMi and have their own media centre interfaces built in. To be honest, I rarely sell NAS boxes and those that I have sold have only been used as a central data storage device so I'm not the best person to ask
.
Hope that helps