The amp is using digital output stage to achieve this power to weight ratio and there is still controversy as to if digital is good enough quality to match analog. I looked at digital amps when considering what to get and found the reviews less than promising. When the 770 came out, I opted to use the 30day trial to test it and after seeing what it could do, I kept it and have been pleased ever since. I have used Carver, Crown, AB, Peavey and other high end amps in the past, all analog and they were all great amps. But for the professional market with a professional price to boot. I would suggest you purchase a model 200 and test it for the 30-day period. If your running ~400W into 4ohms and your set up in in a normal room environment, I cannot imagine you would need more power unless your room is extra large or your speakers efficiency is below 85. In any event, testing with one or two of the model 200's or even testing with the 770 for the trial period will help you understand if they meet your need. Lastly, with this Carver being a digital amp, I would recommend you hear it before you commit to buy. And I would not recommend long term 2ohm operation. We used 2 ohm configs for concerts, but it puts a lot of stress on the amps and they get much hotter than running 4ohm loads. We even tried 1ohm loads on the crowns and they worked (at they time crown was touting this could be done), but that amp was hot enough to fry an egg on. Heat shortens the life of electronics, especially semiconductor junctions which wear out faster with heat and caps that dry out sooner.

Ah, I see as I am writing this post that soundhound has comments about digital amps too which echo some of what I said earlier.