Zotac or other cheap HTPC + fileserver

Hi, I'm hoping someone can help me out in determining what computer will suit my needs, especially in terms of the CPU.

I want a small, cheap PC I can hook up to my TV and use as an HTPC (playing back movies and stuff from a HDD), but also as a backup server and media server.

My plan is to use Win8 Storage Spaces to create a storage pool for backups and media storage, and I'll probably just use external USB drives unless someone gives me a reason not to.

I've been looking at the Zotac website, as they have some pretty nice little machines for relatively cheap. Specifically, the ZOTAC ZBOX nano ID61 PLUS is under $300 and even has a remote for media playback.

My biggest concern with some of these cheap PCs is the processor - that Zotac has a Celeron, and their other machines have Atom or AMD E-350/450 processors, which all seem pretty low-end. Will I have problems playing back video on these processors?

Also, any other advice on machines, components, or ways to set this up are greatly appreciated!

Thanks,
Josh