A while back Korg posted this on their site, It uses Class D ICEpower 125ASX modules in conjunction w/ their NuTubes. While ICEpower modules are typically not bleeding edge like HypeX and Purifi, they're still relatively capable amps w/ decent power and reasonably low distortion. Doesn't seem like they're selling it at this time unfortunately, and not much other info on it, but I thought it would be a cool share. Nutube kits are usually found in commercial or DIY products so maybe they'll offer it as a kit some day~
Nutube Audio Amp | Nutube
www.korgnutube.com