There's been a little progress, now that the PCBs arrived today.
The heat sinks fit nicely, and coupling two 2-port screw terminals together worked out nicely:
Everything fits as it's supposed to, and I like having ceramic components on a PCB. I really think they look the part.
The only thing left to do on the preamp board is fitting the tubes:
There you have it, one preamp fully assembled. Next up is the power supply.