All,
Just ran across this article I thought may be of interest - click me!

Sounds intriguing to me, but I'm not exactly a tech expert on this stuff.

Zetex made the chip I was playing with a few years ago, when I was trying to build my "power DAC".

That article brought back memories, sounds like a lot of the issues I was seeing have been directly addressed. Unfortunately in the elapsed time, HDMI has arrived and brought HDCP with it. The dream of dumping raw PCM from S/PDIF or AES/EBU has passed. The only way to build something cutting edge with this technology is to either integrate it into a full receiver, or implement an HDMI interface. Designing a amp is a relatively easy task (which, by the way, stretched my engineering skills to the limit, I was lucky to have knowledgeable help) compared to those hurtles.

I found these major issues: RF noise (extreme amounts, like my own 200 Watt radio station right at the end of the FM dial), the inability to use feedback to stabilize the output, and finding MOSFET pairs which could switch at 100 MHz while holding back over 100 Watts. It sounds like technology and research have finally provided solutions.