I'm planning to upgrade from a combo to a head & cab rig, but I'm hoping someone can answer a question. Some material I've read tells me to try to match the wattage of my cabs to that of the amp -- or even to use an amp with 2x the wattage of the cabs. But most of the cabs I'm looking at (Eden, SWR, Flite) are 450-500 watts. Does that really mean that to run 2 such 8 ohm cabs, I need an amp that puts out 800-1000 watts at 4 ohm? If I use a smaller amp (e.g., Eden WT400 -- which puts out 400W RMS @ 4 ohm, will the speakers be "underpowered"? And what exactly does "underpowered" really mean? Thanks for the help.