guillaume:
Unfortunately, I do not know enough about the Omega Speaker lines to be able to offer specific speaker recommendations. In fact, I just set up a pair of Hoyt-Benford Type 1 speakers - my first pair of speakers from Louis. However, I have played with multi-channel for over ten years, so I do have some advice, hopefully useful to you.
I went into 5.1 and then 7.1 once with Magnepan speakers because my favorite speakers at that time were Magnepan MG 1.6s. I spent a great deal of money and discovered something interesting about myself. I discovered that I needed the main image (both sound and visual) from the front (left and right) because that was the direction that the editors of the content I was watching/listening to were oriented (NOTE: I still use a "phantom" center channel because I couldn't find one to match the timbre of the MG 1.6s and I don't miss a center at all). The side, back, etc. speakers were to reinforce the main image. So, not only was there only tangential attention paid by the editors of the content to the other channels, but my attention only needed hints of sound to reinforce whatever was going on up front. In other words, 99% of the time, I didn't need fancy speakers for the other speakers. Yes, for an exceptional movie, total immersion into multi-channel sound is interesting. So I go to the movie theater. The rest of the time, a 4.1 channel system is very involving. Frankly, there aren't that many well-edited movies out there and how many times can you watch the same film before you want something different?
I'm trying to make a few points:
First, there is not that much exemplary 5.1 or 7.1 content out there. Kal Rubinson might object that multi-channel audio (especially classical and opera) is available but I'm not sure how much and I don't listen to that kind of music much at all. I would argue that, with a few notable exceptions, there isn't much expertise in multi-channel (or 3-D for video) content so most of what exists is poorly mixed - mostly of the big boom type which doesn't have the same sonic demands. So how often are you going to NEED an exemplary 5.1 or 7.1 system?
Second, my experience has been that I don't need the same quality equipment for all channels. I certainly haven't worked out all the variables required to make a scientific statement about the relative quality of front versus surround, back, etc. speakers, but I think that spending money on the kind of state-of-the-art surround sound setup with mega speakers all around is grievous overkill. I think I seriously over-spent money in my 7.1 channel system.
Third, there are multiple approaches to 7.1 - different strategies. Some are geometric, e.g., based upon a circle with the listener in the center, but I have seen none that take full account of human physiology (ears, ability to sense vibrations through our bodies) AND the physical space within which the system will perform.
With a few relatively low cost additions (two subs, another pair of surround seekers and a pair of Vandersteens 2Cs for rear channels), I split up my large Magnepan 7.1 which became a full 5.1 surround system in someone else's home theater, as well as a killer 2.1 stereo system and a very good 4.1 home theater/multi-channel home theater in my house.
Further, the room where you intend to set up a multi-channel system and where you are going to place speakers in that room are MAJOR considerations, much more important than which speakers. A responsible recommendation for you would require a good understanding of the room including size, nature of wall surface (including openings), budget, etc. - a great deal of effort would be necessary to understand the nature of the sonic environment you want to create. I am certain there are folks much more experienced in this kind of "science" than I am. I learned the hard way (read: expensive and time consuming) that there are no recipes or formulae.
Good luck.
Mike
