Lieven, I have been building the same thing and Dan has helped me out. I can tell you a few things...
This is the short story.
Main Family TV = RiPi 2 w/Openelec-KODI
http://openelec.tv/get-openelec--- notice builds for every OS
-------- this means you can install it on all your devices and stream from local or far.
Now what I figured out about the same time Dan was telling what I needed, and he told me the same thing.... was.... KODI is a kind of a bare bones media center and due to copyright and such, you need to add 3rd party "addons".... of which there are a gazillion.....
I highly recommend you watch/do this... just as a basis to get started....
https://www.youtube.com/watch?v=H8Fgc5IpH30Hard drives.... you are going to want a big drive to store stuff on... just no two ways about it... music, vids, pictures, docs, everything you want your devices to access 'at hand'... honestly I would get 2 drives... one live and one a copy.
Now my router has some USB ports so I can connect a drive there and share it. It can be shared via UPnP Universal Plug n Play... So your devices can see it. Like VLC player and other such media playing progs on your devices. There is an issue with VLC and Win10 just so you know.
Ok, now let's say your router has no usb. Dan turned me on to DietPi and you can share your stuff on it. Again though... and I didn't catch on to this right away... it has to have a USB hard drive connected to install correctly and also serve up all the files. The good news is it will run on one of the older Pi B, B+.. It can assist in "aguiring" etc.. ... I have not got to that yet, as I branched off to my router for some of those duties.
http://dietpi.net/ .. you will need to get Dan to get you squared away on that as I am not real clear yet just how that all works... plus just being Linux is a stumbling block for me... I still don;t take to it easily.
Due to the nature of how all this streaming stuff works.. some of it requires you subscribe to services and of course some is just out there free and some is copyright protected but randomly available. All that is mixed all together within the 'addons" for KODI... so many may wish to use a VPN service.
GMAIL does not play well with VPN services. It thinks you are in another region trying to log in and blocks you until you prove it's really you. Just a heads up on that. VPNs seem to use ip4 but not ip6 such as this one.... although they are supposed to have ip6 next year.
https://nordvpn.com/Dan has a link to a good article on VPNs which I don;t have handy.
Finally you will probably want a cloud backup for your devices once you get all this mess configured. If you don't have a Dropbox account, get one BUT... have Dan send you an invite and both you and he will get an extra 250 to 500 Mb... I could give you one, but get it from Dan so he can bump his up as I am going to be purchasing a 1T upgrade for something else I have going and somehow I signed up to a new account and it's up to almost 6GB now and neither Dan nor I know exactly how that happened... When you sing up though... go through the little tour and deal they present and when finished they will bump your space up.
so in review
Internet
---- Main TV = fast Pi + access to local storage
--------- oh, you will probably need these too...
---------------
http://www.amazon.com/FLIRC-FL-09028-Universal-Receiver-Components/dp/B00BB0ETW8---------------
http://www.amazon.com/Edimax-EW-7811Un-150Mbps-Raspberry-Supports/dp/B003MTTJOY/ref=sr_1_1?s=pc&ie=UTF8&qid=1442238318&sr=1-1&keywords=edimax+wifiYou don't need the FLIRC on them all, just your main TV, the WiFi dongle as needed ( if not wired ).
---- Devices = KODI or some media player to access local home storage
---- Pi = stroage share, acquire, other
--------- Cloud storage for at least Pi backups
------------- Some form of backup for everything
So that's the general layout / flow... but it can be tweaked, streamlined in many ways...
Oh,, and you may want a Pi Radio box and Dan has that info as well... I haven't got to that yet either.
So far I've got
Music Share
KODI and VLC on all my devices and can play all my music on any device
One main KODI install on a Pi2.. have FLIRC but need to plug it in and configure
So Desktop - W7, Laptop W10, Tablet Android for Nook HD+
1 Music Share local
--- next is to connect a USB hub to that port so I can share more drives. then use the second USB port for a network printer ( just found out I can do that hub deal )
I have 2 older Pis left for radio, dietPi duties, etc... so still a ways to go.
Hope that gives you a sort of big picture over view as it's fresh in my mind as I just did it in the last week or so. Dan with have to get you detail stuff.
It's beginning to make sense to me now that I've gotten this far.