Depends on the speaker Tony. An easy 4 like some D9's, no problem. You'll see. Don't take any of the problems I'm having with the Pig pertinent to yours. We are purposely hammering the Pig beyond normal levels to refine this design.
That 400 will let ya know when it's being pushed to hard, it'll start screaming in the output section...
4 ohms will require forced air cooling above moderate levels.