It's my impression that the power supplies matter a little, not a lot, with low-end grunt. When you put Sensation next to ICEBlock, you really hear the umph... but that's a 500% increase in wattage, a huge difference. I think that conventional wisdom that some speakers need tons of juice to flesh out the bottom end, or a powerd sub, holds with the Ushers (like the Ascend Sierras). Duke's AudioKinesis large, high-sensitivity speakers will truly grunt, grunt, grunt with our amps but I've not heard similar low-end rumble on small, low-sensitivity speakers like the ushers. There are trade-offs in efficiency as the box shrinks.