115pro

I bought a Profet 5.1 & have a 411 Pro cab in 4 ohms on order.I've been thinking maybe I should get the 411 cab in 8 ohms & ad a 115 cab later to get the full 500 watts out of my Profet.My question is will the combined power handling of the 2 cabs (1000 watts) be underpowered by the Profet...