How could surround sound be used in an audiophile system?

The Meridian 861 will do all you ask. It will handle/synthessize/balance any number of channels from a stereo source and is capable of handling multichannel inputs if you go that way. Furthermore, I see no valid reason for not going all the way to multichannel since, I suspect, that's where you will get the satisfaction you are driving at.

OTOH, you can get wider spread than 45degrees with correctly set-up decent speakers and center fill should not be a problem either.

Problem 1
Most audiophile music is recorded in 2 channel and was not recorded to be played back in surround.

Problem 2
Even if multi-channel audio evolves (i.e. multi channel SACD or DVD-A) folks are still going to need to run obscene amounts of speaker cable to read speakers. Are rear speakers to be judged the same way we judge the front channels in a hi-end stereo system? This is going to be a rough hurdle to overcome. Even running balanced IC back to monoblock amps that sit next to your rears... How will we judge the sound of the rears?

Conclusion 1
Rears cannot sound as good as front channels. They will always have more often than not always have more distortion and lower sound qualities than front speakers.

Conclusion 2
Multi channel audio is a pipe dream left alone. Until we come up with a way to transmit a signal 30' or so with the same degradation as 10', muilti channel will NEVER have the same fidelty to a source as 2 channel.

Summary
I think you need to examine your system. You did not let us know what your 2 channel setup consists of. You say you are an audiophile, but your description of yourself sounds more like music lover. There are speakers that can cast a soundstage on certain recordings that can fill a better part of half a room (180 degrees) depending on how you set the speakers up. I think you need to re-examine your system and figure out what you may be happier with. I would not knock two channel much, for really good 2 channel can effectively sound like surround if it is recorded in a particular way (out of phase signals can effectively sound like they are coming from directly behind you).

This and $2 will get you a cup of coffee at Starbucks.

Peace.

Keith

It's sad when really good ideas get lost because something supposedly "better" comes along. It's not a question of how could it be used, but how was it used, and why did everyone give up on it? In the '70s and '80s some small companies made available ambiance or "time delay" units which took the main stereo input signal, delayed it and rolled it off, and fed it, either by means of a small built in amp or by use of a small external amp, to smaller, less expensive speakers made by the same manufacturer as the front speakers, or at least of a similar nature to the front speakers. The rear speaker systems were supposed to be set to play just loud enough so that they were not separately audible, and the millisecond delay and rolloff ensured there was no discernible directional sound coming from the rear. The effect was remarkably like sitting in a concert hall, and while it was subtle, it was very significant. The real key was that these units did not require the front channels to go through them, only the rear, fed from the preamp's auxiliary out. The last and best of these units, so far as I know, was a very quiet digital unit, the SONY 505ES, available in the mid-80s, which incorporated the best features of earlier analog units, and which, tweaked and rebuilt, I still use. (From time to time I see one advertised used.) The next year's SONY unit was much more ambitious in delay settings, and did require the front channels to pass through it. Then along came Lexicon, with major programming of delay parameters required, and then home theater, all of which required passing a megabuck front channel signal through a dubious black box. Any number of golden-eared friends and acquaintances have marvelled at how much is lost when I turn off the front channels, even though those consist of megabuck speakers, amps, and signal sources, and the rear channels cost less than 3% of the total system. And as to leaving multichannel sound to the recording engineers, they screwed it up with quad, and does anyone seriously believe they won't again? The choice has become purist audio or ham-fisted multichannel, but it never had to be that way.