I have a LEPA MaxBron in my current machine which powers two nVidia boards. I've been very happy with it's performance.
It has a 6+2 set of connectors. This allows you to fit both the 6 and 8 pin power connectors. If you don't need the full 8 pins, the last two can be detached and don't need to be plugged in.
On top of this, it is fully modular, so you only need to plug in the power lines you need. This saves you trouble with wiring and improves airflow in the machine.
The 800W version of this power supply costs less than $100.
A few other features that are listed that may help your decision (from NewEgg):
- 80 PLUS BRONZE certified with over 88% efficiency
- 6+2P PCI-E connector supplied supporting extreme graphic cards
- Extended CPU connector cable to 23.6" (60cm) facilitates installation with bottom-mounted PSU chassis
- Anti3s Q-Brick design protects power supply from shock, static electricity, and slip