[Zpectre87]

The idea is to build a cheap box that will be the recipient of Steam streaming and also play movies, etc. I'll stream from the "big" desktop. Possibly a DVR too.

I want to know the following:

1) Is a Core i3 enough to do video decoding (1080p/H265) or should I go with a beefier i5?
2) How much RAM? Thinking 4GB@1600MHz here maybe. Forget that, I just realized I have a pair of 4GB Corsair Vengeance chips laying around which I could use.
3) How large does an SSD drive need to be for W8.1 and Kodi? I'd consider OpenELEC as the OS if it could run Steam. I may move to SteamOS later, too.
4) Storage, maybe a 1TB HDD?
5) I plan to use MPC-HC as external player. To add filters, etc. to the picture, do I need the HTPC to have a GPU? How strong does it need to be? I was thinking GTX 750Ti or lower. Or can I somehow use the muscle of the big gaming desktop I have to add the filters through MPC-HC?
6) Emulators, I imagine I'd need to run from the HTPC, right? The software isn't a problem since I'm going to use RetroArch for pretty much everything, so whatever OS I use, they'll work well.

This is important because depending on what I need I can make savings or better balance the machine. The case is not a problem, I'm going with a mini-ATX anyway so it'll be small. May throw in a DVD drive as well, which I already own.

[kuldan]

based on my experience, a current-gen i3 with the included IGP should be able to decode almost anything full Hd you throw at it - and preparing for 4k now is not worth the hassle and the money yet.

If you go the Windows route, 4GB ram should be still enough - I have 4GB in my Ubuntu/Win8.1 dualboot for Kodi/Steam IHS and it works fine (also emulation).
For the SSd, I would suggest 120GB - windows and some small programs can easily take up 60gb for themselves as they grow with updates etc, so based on current SSD prices, paying the 120gb premium over the 60gb model
does not hurt (my ubuntu only kodi setup back in the day had a 40gb ssd, and it ran full due to metadata/artwork downloads..)

If you want to stream, DVR etc - disk size is your concern, I don't have local storage, since I have a 10TB (going to be 22TB soon) NAS in the backend...
About external players I don't know, the internal ones work fine for me.
About emulators, for now: Rom Collection Browser plugin integrating external emulators, in the future the move to retroplayer should be a good option.

For Media Playback, DVD is a non-issue, forget Blu-Ray..but for simple DVD, kodi is more than fine.

[aart3k]

Intel NUC N2820 does just fine for Steam In-home streaming, however it lags in Steam Big Picture mode (just on the menus)