this is 14.9 (non-beta) for linux:
Plan on trying it out.
the hawaii binary should work on tahiti as well.
Indeed it runs, but gives no MH increase :-( Is it 64bits vs 32bits of the one provided by utahjohn?
Mine 64bit windows 14.7RC3 specifically compiled for 280x
Let me know if 14.9 with compiled (14.7) bin helps power consumption if you test it.
Also see
https://bitcointalk.org/index.php?topic=779598.msg9043545#msg9043545 about forcing lower mem clock by vbios mod

Always keep a backup copy of original vbios for each specific card if you need to reflash back to normal for resale ...
If you can't get linux tools to mod the vbios, PM me for options.
Also note that vbios is card mfr specific, so I can't just give a .ROM for Powercolor card and have it work on a different card ...