Not a Vandy owner, and would be interested to read what others have to say. But I have recently moved from smaller to biggger amps, and have been pleased with the relative effortlessness and lack of congestion I seem to hear, at least with less efficient speakers, even where I hadn't sensed the effort and congestion before. Still, I would imagine wattage is not the only, or even the main reason. Bigger power supplies help dynamic headroom and transient response greatly, for instance. Damping factor important too. Anyway, it must certainly be true that if the first watt isn't good, it doesn't matter how many more you have. Of course room size and musical preferences (and damn near everything else) matter too. But my experience has certainly been that, other things equal, bigger equal better, and decidedly not just louder, for amps.
