Any solid state amp that is worth its salt should double the power into 4 ohms,or come close to it!Sorry, but I don't think that's true at all. For example, many McIntosh SS amplifiers use autoformers on the output, so they are rated to deliver the same power regardless of speaker impedance, provided the correct output tap is used. These amplifiers aren't exactly my preference, but I do think they are "worth their salt."
Another example would be Audio Research's DS450, which I think is out of production. These were rated at 450W into 8 ohms and 650W into 4 ohms. I have heard these amplifiers and they sounded a-m-a-z-i-n-g for what they are. Class D, too!