i use a ZyXel NSA 320.
Its a really good peice of kit. got 2 hard drives in there (3tb each) so when you put things onto one hard drive, it mirrors it to the other.
Its got really fast read and write speeds, connected it to a 5 port gigabit switch which is also connected to my main virgin media wireless router, another wireless access point for the ground floor and also my Samsung Smart Tv is linked to the switch too.
My TV plays nearly every format, AVI, MPEG, MP4, MKV, VOB.
All my PCS, laptops and smart phones pick up the nas drive too and plays all the files which I choose to share.
It also has an Itunes Server built in, so you can pick up the songs from your nas drive directly to Itunes.
AND if you know how to port forward, you can access your nas drive from anywhere in the world.
Theres loads you can do with it including Torrent downloads, dropbox, youtube uploads etc. However I havent tried those functions yet.
I hope that helps mate