The korg device has been available in kits for a while. It is used in other devices that have never gained popularity as audiophiles. The Korg device certainly isn't expensive.
The smallest tube amp
This might be the smallest tube amp on the market. Does include a lot of digital things also but interesting concept.
https://www.theverge.com/2021/8/27/22644585/astell-kern-a-ultima-sp2000t-pmp-price-features-triple-a...
https://www.theverge.com/2021/8/27/22644585/astell-kern-a-ultima-sp2000t-pmp-price-features-triple-a...