If you take a look at the pictures, you will notice my power drops from 120v before system is turned on to 115-116v with the Class A Lamm amps powered up. Since my amps are biased Class A and draw 350w each even at idle, not to mention when I hammer my system with some great dynamic range music... This is a voltage sag that doesn't go away, a worst case scenario.... As you can see the PurePower outputs a rock solid 120v.
You can also see that Class A amps present a >70% load on the battery, even at idle. I doubt I'll be listening too long if the power goes out since the battery will be drained rather quickly by the Lamm's.