My current setup:
Mac Mini: For when I want to do really heavy duty things with the TV. Play video games, full web browsing, etc. I have a keyboard and mouse stored underneath my coffee table for this function.
Chromecast: Because mostly, I'm in front of my TV with my laptop and it is easy to just stream over a tab, or pick up my phone and stream over a bit of play music. One of my favourite things to do is put on a YouTube playlist I've made of music. It's like having my own personal MTV.
HTC Wildfire: Yes, one stupidly old phone. However, it's become a remote once the laptop or Mac is streaming. It's size, and quite substantial weight, makes it feel quite good as a very basic media centre remote.
I do almost everything via streaming Netflix, so I've never had a need for any kind of media server. I did actually use Plex in the past, but I found it was prone to breaking (things have probably improved in the last two years though)