The PCBs have arrived, and they look great. I normally use DirtyPCB for my boards, but I tried EasyEDA for this run and I'm quite pleased - $90 for six 100x150mm four-layer boards, plus four-day shipping.
I'm planning on assembling them over the next few weeks. I have very limited experience working with SMD components, and even then only with fairly large components, so I'm going through a few practice kits before I try my hand at the real thing. In the meantime, I'm still working on v5 of the ISA, which hopefully will be more-or-less locked in by the time this board is up and running.