Whats the MS equivalent of Apple TV?

is there an equivalent to Apple TV which lets me do exactly the same with my Windows Phone and Windows 8 PC/Tablet (replace the shitty Samsung Software & streaming content from other devices)?

Maybe even with some more features like

- plugging external HDDs into the box so i can access them via TV AND the PC, so i can put new files on it and have imediate access to them via TV.

- plugging my stereo into the box so i can stream music to it via WiFi. That way i can listen to music without my TV or PC being actually on.

I don't know if Apple TV does the stuff i mentioned above but i'd sure love it. As Apple TV isn't really compatible with all my stuff (Xbox, Windows Phone, Windows 8 PC), i'd really love a box which fits right into the MS ecosystem.

I got an XBox but i guess i can't stream stuff from my (windows) phone to the Xbox (yet) and also, the music thing wouldnt work as i can't plug my stereo into the Xbox.

What do you guys think? What would be the best way to setup my home entertainment network? Buy i new ethernet-ready HDD? Buy apple tv equivalent? Something else?

Current equipment:
Samsung 55" Series8
Xbox 360
WIndows 8 PC
Samsung Galaxy Tab 2 (will be replaced with a surface RT soon enough)
Stereos (currently plugged into the TV, though thats not good for listening to music because the TV has to be on, and i have to access the music library on my PC (which also has to be on) via the shitty Samsung software on my TV)

I'd appreciaty any help and tips on this one. <3