I think you're clustering ICE with Class D as in ICE is the route and Class D is just part of it, it's the other way around. ICEpower is a Bang & Olufsen design that takes advantage of the efficiency of switching amplifier technology (Class D, sometimes refereed to as Digital). ICEpower has to be licensed from B&O for use by other manufacturers, such as the Pioneer Elite SC-07 and SC-27 receivers. Class D and other switching amplifier technology has been evolving over the past 10 years at a rapid rate. ICEpower was one of the first well known breakthroughs in home audio amplifier technology where the industry began to realize that this technology wasn't just for cheap equipment, and had a place in the high end audio market.
The Yamaha RX-V665 is class A/B as another member pointed out. Be that as it may, the effectiveness of the amplifier in this receiver is, in my humble opinion, poor at this price point. The receiver has a small power supply compared to it's predecessor and uses integrated output devices instead of bipolar discrete ones. This is common on cheap audio equipment, however before this model the RX-V6** series had always used discrete output devices. Simply put, the RX-V**5 from last year are one of the worst examples of home theater receivers that Yamaha has put out on the shelves for sale. They are ugly, and they use cheap parts.
I'd advise against this model unless the price is just amazing. I'd rather own the RX-V663 or RX-V863 from the lineup before.
