I did try running a minimal configuration (in the case) with only the audio header, memory and CPU attached. I could not get the video cards to be recognized in the PCIe slot with this configuration.
I'm unclear about what would be accomplished by trying the same thing with only a single memory stick? I'm also not certain that firmware updates on the video cards are warranted as they work in a much older generation M/B (Asus P5LP-LE) and also work in another M/B with an H77 chipset (see the following paragraph).
I installed an ASRock H77 Pro-M motherboard with all of the same hardware I had on the Intel DH77EB. The ASRock M/B recognized the video cards in its PCIe 16x slot without a problem. I was able to complete my build using the ASRock M/B.
It would seem that this would suggest the Intel board is defective. I am initiating the warranty return process.
Thanks for your suggestions.