A colleague suggested that I try each RAM module separately. One RAM module worked fine, while the other presented the same no-boot issue.
Conclusion: One of the two RAM modules is defective.
I'm now opening an RMA with Corsair as the RAM has a lifetime warranty.
I looked into 2x4GB modules of PC6400 RAM ... whoa!! nope ... won't go up to $100 / module (I remember paying $45 per MB for my old 286 mobo).
Thanks for the answer - it was a good idea. I had already verified the rev 2.0 of the mobo was certified; mine is rev 1.1.