To the folks who suggested Kalroth's cgminer with the xintensity feature, you have my thanks.  His version is better in pretty much every way, near as I can tell.  I have increased hash rates across the board.  And I can run my Linux desktop on top of a 7950 doing 600kh/s without it seeming lagged.

Incidentally, I have my 7950's running with xintensity 4, gpu-threads 2, and shaders 1792.  280x's the same except shaders 2048.

Oh, and with this version, I can underclock the memory on my 7950's all the way down to 900Mhz with no change in hash rate, which saves a significant amount of power according to my kill-a-watt.  The 280x's wouldn't accept anything but the default memory clock without throwing a fit, however.