The X-12 preamp kits are now on sale.
I updated the X-12 PDF guide and explained more about the option of using PDIP8 chips and DOA chips.
key is using MillMax socket pins on the board. This will allow you to
quickly remove the PDIP8 chips, insert your DOA chips and do some
listening tests. The DOA chip sits well above the IC sockets. You'd
have to remove the PDIP chip though if you want to use DOAs.
Here's the latest photo of the X-12 preamp using an API 2520 clone Discrete Op Amp.