So all is good with single card?
Here's mine with cpu/cache at only 4.5 / 4.375, 25k should be doable at 4.6 I think so something is wrong for sure.
http://hwbot.org/submission/2705326_l0ud_sil3nc3_3dmark11___performance_geforce_gtx_980_23526_marks
Very nice, the Strix has a very efficient bios, even for many other vendors cards. I have not even tried to install XP with the 980 yet, but 1500 memory clocks are a problem that needs to be fixed for sure.