All you need is Ram (So-dimm DDR3) and mSata. You can get 8gig ddr3 sodimms cheap from MM, and even brand new 480gig Crucial M5 mSatas for £159 quid.
In regards to the silence factor well its using the new haswell chip, and they have improved the thermal and heatsink design so hopefully the fan will be nice and silent. Am sure over time there will be many 3rd party passive heatsink nuc cases for it also.
Even ones slightly larger to allow for the use of a 2.5 ssd or 2tb hopefully.
I think Raspberry Pi is great for just streaming but your limited, an intel nuc will handle anything you throw at it. Most likely 30gig Mkvs, 720p/1080p via a streaming website like youtube or other. You have option to use windows 8.1/Linux and enjoy full driver support, same HD quality you would get from your pc... but yeah cost 10x more!