It really depends on what you are trying to do....

For instance overpowering daylight to really darken up the ambient needs a fair amount of power BUT depending on how fast your camera syncs, what modifier you are using and how large you subject is make a HUGE difference and will have more of an effect than going from an AB800 to an AB1600.

I use the WL x1600's and my digital camera syncs at 1/250th... even outside for fill, or with a small box to highlight a face use them set to 1/4 power (in this setting its the same as an AB400) with an umbrella and I am really trying to darken up the environment I use 1600 and when its real bright out wishing I could sync at 1/500th

You might also try Long Throw reflector or PLM...these are designed to get uber-output from a standard or lower-power strobe. We shoot horse shows in a covered arena with serious backlighting, and prior to using the Long Throws were suffering from noise issues with the higher ISO we were required to use in order to get the shutter and f stop the action called for. You might try either of these to boost the output of your 800's. Good luck.

B800 42" PLM 10ft 1/2 power @ ISO100 = F16 bring it closer and get more power! Your light modifier will go a long way in determining how much power you have at your disposal!

Silver PLM is the magic needed to overpower the sun will smallish flash units. I get f22 at 10', ISO100 from 320WS AB800. With a softbox at this distance you'll get f8 to f11.