Not a good idea but if your amp is stable at the ohm load present. I wouldnt run the three over 900 as your amp has no way to know there different if you try to run at the 1100 watt rms the subs r rated youll likely ruin the weaker sub. I would just run the rfs on the 800rms there rated from what your saying wattage wise you would only end up 100 watts more running the third sub and youll stay away from a strange ohm load