Stereo mode # 5 channel mode.
What is is rated in the stereo mode?
What is it rated in the five channel mode?
When you level the playing field and compare the with the same criteria (stereo to stereo, 5 channel to 5 channel), I doubt the NAD will still be "twise stronger".
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This is not to say I don't like NAD. I do, very much, but you've got to know how to read specs before blindly quoting power ratings. The can be very misleading to the uninitiated. Once you know that, you'll see that NAD actually is very honest, and conservative, in their ratings.
Here's a link to the
NAD 747. You'll note that in all channels mode it's rated at an honest 70 wpc. While this is a small difference and most likely it's a better unit, it's not an earth-shattering difference in power output from what you already have.