I don't know the exact ratio, but tubes will have more power than solid state of equal wattage.

I would definitely stay away from 1.5-3 WPC if you plan on incorporating it into your HT. There is not enough headroom to handle the dynamic peaks.

Generally speaking, that kind of small wattage pretty much requires highly sensitive speakers, and/or moderate listening levels.

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"Nothin' up my sleeve. . ." --Bullwinkle J. Moose