Could part of the issue be manufacturers trying to push more out of the 8 ohm value than they used to? Say they made an amp like the example, but instead tried to get up to 250 or 300 watts @ 8 ohms instead of 200. Then they're still kind of limited to the 400 or barely over at 4 ohms.

painttoad, you probably already see this, but it would be better to use the amp's value at the 4 ohm load instead of just doubling the 8 ohm value for the reasons we are discussing now.