urgh. just typed out a huge reply to this and then lost it. short version:

-DX9 was absolute garbage on AMD. Crash crash crash. that's what happens with an ancient standard that no developers use anymore.
-Your 2 290xs sound like they're keeping up better than my 2 7970s
-DX11 should fix crash problems entirely due to not ancient standard. So far I can max out 1080p with high frame rate on DX11 easily, no crashes.