I am sure you can get a good bit more out of them. If you clip the signal a little it will not be harmful to the subs, only when you run 10-20% distortion will you start to mess up the sub. And I think you would get more power out of them running them individually and matching the gains, not to mention if you get the voltage up to 14v. But those are good results for a completely clean signal and 13v.