I have said this many times before. At the low end of the price spectrum, an AVR is designed to deliver movies well. So it will be stupid to expect it to play justice to music as well. That is not the primary intention of the designer. If you need good music at that price level, it is always better to have a separate two channel amp.
But as you move up the price spectrum, the designer's have the freedom to do what they like. At the reference levels, it will become very difficult to differentiate between the sound signature of an AVR from that of an equally priced two channel system. Actually an AVR has a commercial advantage in the sense it can use better components simply because it sells more pieces. Things such as Burr Brown, Cirrus Logic, and other DACs are being used more frequently. Many AVRs have separate paths for each channel, in essence acting as mono blocks for each channel.
Over the last few weeks, using the Audire IO2s this has been proved quite effectively to me and a few others. The Onkyo 875 was able to proudly compete with a Cayin tube amp and a NAD 350. We will be comparing with other amps over the next few weeks, including, hopefully, the Lyrita tube amp.
PS, the Arcam AVR600 now sells at 3.24 lakhs !!!! Sigh!!!
Cheers