65 inch screen and size reasonably close so L/R speakers are only just to the sides of the screen with seating about 1.5 the distance between the speaker sway from the screen.
I use my Oppo 205 to downmix and just use two channel for everything. My main speakers are Stirling LS3/5as and AB-2 bass extenders, both with high-quality external crossovers, and the soundstage and imaging means vocal/effect placement is spot on. It would be awkward/expensive to replicate that with a centre of the same quality and there's no need. Plus I would have to trade mu miniDSP SHD for a multichannel version.
I don't use rear channels - I find too much of a disconnect between the 2D screen in front of me, which is wide but does not fill my whole field of vision, and the attempt to create a 3D audio space, I'd rather my brain just process 2D, and the stereo effect makes a pretty good attempt at throwing sounds around the soundstage anyway.
Also have some subs there as well.