PCB's arrived a week ago, but I got swamped by work :/
The PCB's look exactly like I layed out. Can't wait to get parts and test them!
Also made a bill of materials. (and uploaded it to the "files" section) Looks like my one-off price is $70. That's a good bit higher than I was hoping. After the first channel, about $20/channel can be saved by taking advantage of the ability to stack the post-amplifier PCB. Using a cheaper PCB vendor and shrinking the pre-amp half of the PCB would also be able to save about $10/pcb. Finally, a post-amplifier made from discrete transistors or RF parts should be able to cut $5-8/board from the BOM. But I'd only attempt that if volume is large enough to justify the extra work. (and of course purchasing volume should be able to save 10-50% off whatever is left)