I rarely use center channel with processor

@erik_squires 

+1

I have tried home theater without a center channel (I have all the same B&W 805 speakers... the center channel is a center channel one) and the difference has been obvious and poor. The lack of energy coming from the center was profound. 

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.

@andrewdrummond 

Placement of rear speakers I think is really important. Not so much in the back of the room but on the sides so the sound is received directly to the side of your head. 

But I find that without rear speakers you still get sound from behind you from the reflections which Is fine, and sometimes preferable. But even with that I’m not a big fan of rear speakers because the quality the recordings is seldom that good to take advantage of it.

Sure occasionally you get targeted rear channel effects but it’s kind of annoying most of the time. 

subwoofers and main speakers that’s all you need. 

I should add that I did upgrade my center in the past year.  The original one was  rather smaller, 2 way which couldn't go very deep.  Went from dual 5" woofers to dual 6.5" and a low cut off of around 100 Hz to 60 Hz, and passive to active. 

The difference in the sense of fullness and weight was noticeable. After the upgrade though I can't tell if the center is on or off except sitting off-axis, so for this reason I think if the OP is hearing a big difference, his center may not be fully set up yet. 

@erik_squires 

When I listen to the system and the center is off the sound appears to be coming from the center so I think it's set up correctly.

I think people buy centers because it seems to be a necessary thing to do.  If you feel you need to buy a center buy something that's meaningful otherwise just rely on the mains.