[Of course, Tripath is interested in selling 25K chips not bothering with a guy who bought one board.]
I would tend to cut them some slack. Judging by their financial starements Tripath, the company, seems to be fighting for its life.
What speakers are you driving? I would think that relatively inefficient speakers, complicated crossovers, etc. would benefit from the increase in power at the higher voltage.
FWIW, I used a RS wall wart for about a week. It was supposed to be 12V but wound up measuring 14.8. The unit ran warm (not hot). This was almost 2 months ago. It has been running about 8 hours a day since (in an office system) off a 12V SLA and still plays great. It definitely runs cooler.
The 2024 does seem to be a great chip. Sharp is apparently putting it into some of its new LCD TVs.