Still HCC seems to be the most profitable since you can finish them very quickly, even with a slow GPU you're looking at >5 points/minute. A WU of FA@H gave me 378 but took 2 hours (3.14 points / minute). Anyway to apply to the challenge you have to turn in CPU results as well.
My other rigs:
OCTANUX - Conroe865PE - QX6800 - 4GB OCZ Platinum EL - HIS HD4670 AGP - SB Audigy 2 ZS - BFG PPU
phenomenal - AM2NF3-VSTA - 965BE - 8GB OCZ Platinum LV - HIS HD3850 AGP - SB X-Fi - Asus PPU - *WIP*
Green Tea - 939A8X-M - FX60 - 4GB OCZ Platinum EL - 7950GT AGP
Re-build - CT-6VTA2 - PIII 600E - 384MB PC133 - Voodoo 5500 AGP - SB16 ISA
BLUELINE - H61M-GE - PDC G645 - 8GB DDR3-1333 - Powercolor HD7750 - 2xTV Wonder 650