Matt, the second thing to bear in mind is that the setting of the level (volume) control is nothing directly to do with the max power output of the amp. The level setting is determined by the sensitivity of your speakers (how loud they play at 1W), the gain of your electronics chain (what input voltage or recorded level is needed to swing the power amp at 1W), and of course, your own listening habits. The maximum available power of the amp does not appear here as a factor.
With regard to the tube amps, it is true that in most tube amps clipping occurs very gradually, and when they start to clip, the quality of distortions is much less objectionable (and much less harmful to speakers because the distortions don't contain much of high-frequency/ultrasonic components). As a result, they produce a quite acceptable sound quality even at way above the rated power.
