I think I found my problem when I went to pull my second card out. The second card wasn't being fully seated in the pcie slot. It overhangs my front panel headers by about a quarter of an inch and the card isn't locking in because the header connections are slightly too high. If I remove the connectors, it seats just fine....what to do about that??
Yep, that was the problem. After slightly bending the header connectors, the card seated okay and it was immediately recognized and it enabled crossfire when I booted ^_^