While not disagreeing with any of the above. It does depend on your needs.
I had a Raspberry Pi anyway, and it is under £30 to buy anyway. If you like playing around with such things, will give hours of playing with anyway.
I am running Raspbmc on it with the Amber theme. It works great, and gradually migrating all my media across to it.
The vast majority of my video’s are 1080 x720 at best, so if t cannot cope with higher HD, that does not worry me.
XBMC does take some learning, sometimes frustrating, but fun also.
Additionally there are loads of add-on’s, so if you’re are in the UK can do i-player, and other streaming services etc.
I didn’t need to buy anything else, thought I might need a keyboard etc, but use the yatsi remote app.
It plugged into the network via mains homeplug gadget, with a 2T hard disk in the usb socket. So did not need to buy anything else.
All for under £30