So how about my getting a spare Dell Venue Pro 8 (Atom Z3740D), connecting it to a monitor, keyboard and mouse and using it as a desktop?
I can just pop in microSD cards when I need to add more disk space.
(I'm currently using an AOpen i855GMEm-LFS with Pentium-M CPU 1.86GHz and WinXP)
Set aside I don't think you can use an external monitor with it, but that tablet is, ahem, a tablet.
So, from a desktop perspective, it's low on RAM, it's low on storage, and it's not expandable (not to mention it's low on performance). Does it actually fit your needs? I can't help about that.
On the other hand, I said there are no really close siblings, but most of the Z-series features are meant for tablets, so that a J1900 (if you need transcoding) or a N2910 (if you don't need the QuickSync feature) are more probably that not better CPUs than the Z3740D: just they can't compare to this latter with reference to heat (but they are low on heat too, when compared to desktop CPUs).
If I can take the liberty to say, probably you have to write down all your actual requirements, rather than trying to track down that specific Atom.