Well, I don't feel like this is any closure to the tale, but here's the state of things. I put everything back together and, despite cleaning the board thoroughly with isopropyl alcohol, I continued to get the Chime of Death when booting. So, in a desperate attempt, I installed and removed the RAM about a dozen times (something I'd tried many times before). Suddenly the machine booted. I've restarted a bunch of times and it seems to continue working. Anyway - I have no idea what it is. It's kind of annoying that I haven't sourced the root of the problem, but I guess I should be glad the Q700 is working? :-/