Hi, just a thought, in skimming over these comments I didn't see anyone mention the actual current output of amps as a factor, the reason a Sony 100watt amp will not drive speakers as well as most "high-end" 100watt amps is down to it's current limitations. Most people seem to think distortion = loud as in many demo's I have performed with speakers people keep saying "go louder" and don't realise they are having to shout very loudly to get their message across then the speaker hit's it's end-stops and they are all disappointed because they think the speaker was feeble because it didn't go all harsh and crappy sounding. This is where good amps (such as class-a and valves) outperform lower quality ones because they don't distort with their high current keeping the speaker under control. Next time you look at an amps power rating bear this in mind as this is usually the reason some 250watt amps dont work as well as some 50watt ones (liken it to torque and horsepower in cars... a Honda with a 2 litre engine pumping out 200hp and a car of a similar weight and hp but with a 5.7 V8 will both have advantages but you can bet the big V8 will cruise at 90mph a lot better than the Honda if the gearing was the same...)

So sometimes an amp with a low wattage will go much louder without distortion than a high wattage model, I know this is a little off topic but it is an often overlooked point that should be considered more often. You can have a speaker pumping out 90 decibels of horrible distortion which will not be pleasant to listen to at all or you could have one putting out a pure and clean 100 decibels which you could probably listen to for much longer...