A "dumb" question about power ratings?

Kurt, I salute you on asking your question instead of making an assumption. First, a minor clarification. Your Gem's have an efficiency of 87 dB for one watt input at one meter. They have a "nominal" impedance of 6 ohms, and a minimum impedance of 4 ohms. In other words, they are of pretty much average efficiency and a little more difficult load than average, but no sweat for an amp in the league of Levinson or Ayre or Pass. Amplifier power for stereo amplifiers is customarily per channel, unless otherwise specified. Thus, your "125 watt" Levinson amp is 125 watts per channel, and so on. The question of how much power is enough depends more on your listening tastes and room. For example, say you like orchestral music at the kind of volume you'd get halfway back in a concert hall, maybe 95 dB peaks. And, let's say you sit 12 feet from your speakers. We're going to ignore some factors to make this simple. Okay, one of your speakers will give you 87 dB at 3 feet (one meter, give or take). Two of them, each getting one watt input, will give you 93 dB at three feet. Back up to 12 feet, and the sound pressure level will have fallen off to 87 dB. This is fairly loud, but remember we want peaks of 95 dB. Now here comes the important part. When we increase the wattage input by a factor of ten, we increase the sound pressure level by ten decibels. So at 10 watts per channel input we get 97 dB at our listening chair, at 100 watts input we get 107 dB, and at 1000 watts input we get 117 dB. So you can see that a 15 watt tube amp would give us our 95 dB. I'd like a bit more reserve power for occasional forays into hard rock, but I'd rather have 15 real good watts than 1500 crummy ones. Of the amplifier brands you mention, the Pass Aleph series would be my first choice. Hope this helps.

"Loud" is herby defined as 85 dB at the listening position. "Twice as Loud" is 95 dB. "D*@# Loud" is 105 dB. And "TOO D@#& Loud" is 115 dB. Okay you nailed me on the "good watt/crummy watt" thing. I'll take a shot at it, but I can't back up anything I'm going to say with math. Some amplifiers make you tired of listening, make the music sound grainy or harsh, give you a headache, have no life. You want to turn the volume up so you can hear what's happening in the music. And other amplifiers (often with much higher distortion figures) sound liquid, musical, full of life and energy, like this is easy and they're having fun doing it. You enjoy the music immensely at all volume levels. It's hard to pin down just what the difference is. It's more of a feeling than a tonal difference. But one thing is for sure - we really don't have a consensus on which measurements are of sonic significance. So this is where trusting your ears (and feelings) comes in. Yes, amplifiers do sound different. The difference may be subtle, but it's profound. In my experience a really beefy power supply is very important. I personally lean toward output transformerless (OTL) and single-ended triode (SET) tube amps, but I've heard excellent amps of many different types. Amps that run Class A, or that use little or no negative feedback, often sound (or feel) more musical to me. Okay there's another, more empirical way to predict sound quality - how many pounds an amplifier weighs per watt of output. The heavier, the better. And sadly often the more dollars per watt the better. Yes all things being equal having twice the power will give you a greater sense of ease. The thing is, all these generalities are nice until you get down to figuring out what you can buy with $1500 (or whatever your budget is). Then the more experience you have (not the more cheap [ahem!] advice you listen to), the better choice you will make. I hope you can borrow and listen to a bunch of different amps in your system and come to very different conclusions from the ones I have, because my conclusions have cost me dearly.