Well, I'm back from vacation, and all of the components have finally arrived. I'm getting ready to transition to the build phase pretty soon here! I'm working now on finalizing the layout. There are other decent looking layouts posted elsewhere on the web.. see for instance the very close copy of the original layout that was worked out over at recproaudio. It looks to be a decent layout, but I think I may be able to do better. In any case, I wanted to add regulated DC for the heaters to make sure that the noise floor is at an absolute minimum. That alone calls for a certain amount of rejiggering.
Anyway, there are a few more iterations left before beginning to solder, but I'm thinking that the basic layout will look something like this: