So, at least for the 2 manufacturers above, higher power is possible & better :-) It is only the cost that will be the negative aspect.From a designer/manufacturing/engineering point of view I can tell you that this is simply incorrect. Its much easier to build a low power amp than a large one, and even though in a larger amp you can have the advantage of paralleled devices to minimize individual device aberrations, the simple fact is that the added complexity is a **frequent** downfall!
I've also mentioned several times on this thread one of the peskier issues dealing with the myth of more power which is outlined in @pragmasi and @shahram 's posts above. If the amp is always operating ***below*** its minimum distortion level, you won't be hearing the best out of the amp or the speaker. For this reason the amplifier power has to be matched properly to the speaker efficiency such that the amplifier is doing its best work at normal listening levels. This isn't ideal but we live in a real world that does not care what we humans regard as ideal. So you have to be pragmatic and recognize that amps aren't perfect!
Now anyone whose read this far may have picked up on something- that in addition to a distinct advantage in terms of sound quality to matching the amp and speaker (a powerful amp working with a lower efficiency speaker and a higher efficiency speaker is better off with a lower powered amp), that also unlimited sound pressures are often not possible in many listening environments. Since thermal compression in loudspeakers is a very real thing, there is an obvious advantage to working with easier to drive speakers since they will play the dynamics in the recording better. At the same time because the amp isn't working as hard, it won't have to make as much distortion either.