Anon, I have the Series 6 55" LCD - bought it online and had it delivered from Melbourne. The interface is just trying to be fancier than it is utilitarian and not particularly slick - some of the ATV/XBMC interfaces were really attractive *and* smarter when it came to browsing. With the Samsung, you're not working against it all the time, but it could be better. Interface seems to be something all these devices (set top boxes, etc) get really wrong - our DVD player accepts a USB stick and the browsing interface for that is akin to Norton Commander from 20 years ago.
Back to the Samsung - the picture itself is excellent. There are two USB ports so we leave the two main drives plugged into those. Seems to play most things we've thrown at it so far. It also has some other connectivity options (have got a wireless dongle so it will show YouTube, etc) but I haven't really bothered exploring those.
One of my drives at home is a basic NAS and I had another at the office which died and I've replaced with a QNAP two-drive NAS. You could combine your four drives into two of those? They have built in iTunes server along with a bunch of other things I haven't experimented with yet.