In any case, the i3-3220 mini-pc I built boots in less than 4 seconds which is much faster than any media player and faster than my about $5500 PC and auto-boots from cold and plays eveything flawlessly - and I mean EVERYTHING. I put Windows 7 on it because it was significantly cheaper than the client paying me to configure OpenELEC.
None of the Android media players are any good. They can't play back crap, and neither will XBMC on Android for the foreseeable future which includes the OUYA (which I am a supporter of) because the on-board graphics cannot play back high-bitrate 1080p content which you clearly want. Tegra 3 CANNOT even play back MKV natively, period.
Now, if I knew about this QNAP device, I would have totally bought that, though. I feel like a real dummy for not knowing about it... how come I didn't know about it? I hope it's a new thing, I didn't know such NASes existed.
Otherwise an HTPC of some form (the Xtreamer Ultra IS an htpc) is what is required to run XBMC right and it is worth it. Honestly, if you do it properly, an HTPC is so easy to run these days with your android/iOS device as the remote. And if you install something like an iBoot G2 it will automatically power off/reboot it (dependent on setting up your motherboard's BIOS as well) for you in the unlikely event of a crash, in case pressing the reset button on the htpc is too hard/difficult or you've installed it somewhere hard to get to.
If you can afford it, and yuou are a movie fanatatic with a huge library, there is no worthy alternative to XBMC, not by a LONG shot.
And a Mac Mini is no cheaper than building an HTPC and it'll be slower to boot and I would not vouch for the playback compared to an htpc. If you want something that small/quiet and already have a NAS, then get the Intel NUC.