I personally chose two pair of FXi3 speakers because I got them for a song from Polk as refurb speakers.. got em, looked brand new to me. I wanted the KEF Reference TDM34DS di-poles, but they are nearly impossible to find now, and I'm not sure the current incarnations of their "DS" line of Ref speakers would be well-matched to my system, nor are they really within my price range, at around $3,000/pair.
That said, what I didn't note, was that prior to my current setup, in my current home, I was in a much larger home, wehre I had a lot more room to play with speaker positioning, and used one pair of the bi
-pole speakers as back surrounds, mounted higher on the wall as shown in the above pics, and used a matching pair of the same speaker, set to di
-pole, on either side of my loveseat, used as the central position in front of the screen, about 4 feet away from each side or arm rest of the couch, on 36" Sanus natural foundation stands. They worked very well for 7.1, and I at no time felt a desire to swap them for a studio-monitor type bookshelf pointsource speaker instead of what I have.
If it will work in your situation, depends on a lot of factors. power applied, speakers chosen, room acoustics and treatment, source material you're viewing, and so forth. I can't tell you for sure what will sound best to your ears, as that's purely subjective anyway, but for me it worked great.
Oh, also, the FXi3 is not a 5-way speaker, nor does it have any speakers on the back side of the enclosure, so I can't really offer you anything on that front.
This is the FXi3: