No, it is a complete myth that underpowering "damages speakers". This is a total newb myth, that spreads like wildfire.
This is because you can blow a speaker by having the gain too high, on any size amp. So newbs and people who dont know about car audio jack up the gain and blow subs. This is often a result of too small an amp, which doesnt produce enough bass for the listener, so he jacks the gain up. Think about it ---you can listen to your radio all day at 1/4 volume, which would be severely "underpowering" your speakers... no ill effects.
It will be FINE. As long as your L7 is a dual 4 ohm version. If you have the dual 2 ohm version, the amp will only make 300 watts. Set the gain correctly.
