IMO “ideal” is a relative term here. AFAIK most sound engineers mix their channels so that most of the LFE is coming from the LFE channel and Mains. I even have some Blu-ray 7.1 audio that has all the front channel information mixed into the Mains with only some reverb and ambient stuff coming from the center channel.
Also when using DSP like Dolby PLIIx the information being sent to the surrounds and rear is the ambient (out of phase) information which most people find is better reproduced using di-pole or bi-pole speakers.
I did a lot of research and experimentation into getting what you term the “ideal” setup and found the only place using another full range speaker improved the imaging was the center channel. I found that using bi-pole speakers as surround and rear is far superior for my uses than using either full range or direct radiating bookshelf speakers.
Also having identical full range speakers all around is usually considered the ideal for multi-channel music and not HT. like I mentioned AFAIK most movies are mixed to account for the types of speakers people typically have in various positions. Even most of my music SACDs DVD-As and concert DVDs just have ambient sounds of the venue mixed into the surround channels.
If I can find it, on a different computer, I have a link to an article that makes a very good argument for why using either identical bookshelf speakers crossed over to a subwoofer is probably the best bet for most people for multi-channel music. And that for a combined music HT system that using di/bi-pole speakers as surrounds and rears may even be a better option.
In short even if money were no issue I still wouldn’t upgrade my QS8 surround/rears to M80s since the QS8s are better designed for those duties.
One member here, Onn, does have M80s surrounds and might be able to add his opinion of their value.
