Since I bought a couple of better front speakes for two channel use I was able to move my front Mirage Omnisats into service to complete my 7.1 setup. I'm sure the placement is not ideal but I have a pretty typical rectangular room and it seems to provide a fuller sound for surround purposes.
The nice thing about the little Omnisats is that they are cheap (and very good) and can be easily mounted on the ceiling. They also are omni-directional and provide a great sensation of space or ambience. The first track of The Animatrix DVD is astonishing with a full 7.1 set up.
Having said all that you get 90% of the effect with 5.1 and I still prefer two channel listening for music (except for the odd SACD or DVD-A).
For the cost of two Omnisats ($58 each?!) and $20 for wire you might as well use those extra two channels since you paid for them!
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1070, Arcam CD73T, Pioneer DV46-AV, Project Xpression-Grado Red-NAD PP2, Monster HT1600, Wharfedale 8.3 Diamond, Mirage OM200 sub, Omnisat Micros x 5, homemade speaker cables, Dell Axim 51v remote