Hi Mike.
First, some background from me.
I'm a fan of Mirage speakers. I have a pair of their M760's that I bought back in 1989. They're typical box type floorstanders. When I listened to them at the dealer, I like them right away as they sounded great. Surprisingly, they sounded even better when I set them up at home. I then added two pair of the M260's for rear surrounds and front presence (used with a Yamaha stand alone DSP unit I had at the time). I'm still using the M760's now in a room that's terrible as far as proper speaker placement goes due to space limitations. I'm using them with a Mirage Omnisat v2 center and two Omnisat v2 sats for surrounds (the surrounds are mounted on Mirage stands about a foot from each side of the sofa), and a Mirage S12 sub. Receiver is a Yamaha RX-V2700.
Given the lousy room constraints, the system sounds terrific.
Before I connected the 760's, I ran a pair of the Omnisat v2 floorstanders for a while. They also sounded great. Not the same as the 760's of course, but that's to be expected given the differences in the two (bass is quite good from the Omnisats, but they really should be used with a sub. With the 760's, I really don't *need* a sub). Again, with no room for adjusting placement on the Omnisats, I was very pleased with the results. I have a similar situation as you. The sidewall on the right is about three feet away, and the sidewall on the left is about five feet away.
I'm building a new house, and the living room will be much bigger, and will allow for much better speaker placement. However, while the left sidewall will be about two to two and a half feet from the left speaker, the right sidewall will be about five to six feet from the right speaker; very similar to your room. I have no doubt that my old 760's will be fine, but I'll be looking at new mains for the new house. The 760's still look and sound like new, but they are, in the end, black boxes. I'd like something with a nicer finish. So I've been considering the new Mirage OMD-15's in rosewood.
I called Mirage and spoke to their product manager (Martin) about using the OMD-15's in my new house as I have the exact same concern as you. Martin felt I'd have no problem, and I suspect he's right. And keeping in mind that adjustments such as eq and levels can be made to each individual speaker via the receiver, I'm pretty confident the the OMD-15's will be fine in my room and the Omnisats in yours. Of course I have the advantage of already owning the Omnisats to try. So, I'd say if you want to try them, order from a good outfit like Crutchfield, so you can return them if you decide you don't like them. The only money you'll risk is the return shipping.
HTH
Jack