And when I say professional-grade, I mean sturdy, expandable, and hackable to the core. Designed for Linux/*BSD first, that still runs Windows if the end user wants to install it themselves. If something like the Novena can succeed with a 1.2GHz ARM, I'll be damned if something similar with a quadcore x86 wouldn't do a hell of a lot better. It may bring in small change to a Dell of the world, but there has to be _somebody_ in China who would think otherwise.
The way to do it, I think, would be through a crowd-funding type of platform. 3D print a prototype, prove the sales are there, and then you can spend the money on design and tooling for manufacturing.
Every attempt I've seen, though, has either failed, or fallen prey to the lock-in-based lure of Microsoft.
Hardware margins are thin, unless you're Apple.