I found the center spread feature to be a no-man's land. It ruins the potential benefits of a center channel without sounding any better than 2 channel. I suppose it could work in situations where you are frequently off axis and need to stabilize the image in the center better, but the center channel is drawing too much attention to itself. I know some people like to just double up on the stereo speakers, L, L, R, R an inboard and outboard set. I've tried this and it really is a richer sound in some ways. It changes a lot when you move around, which can allow you to find a tone you like by just moving!Exactly my experience as well.
There is a "center spread" feature in the Dolby upmixer (should be in the settings of every Dolby-licensed AVR), it absolutely must be ON. But it doesn't cure the problem, only lessens it. The soundstage of upmixed music is still constricted by the center channel.
My center speaker (retired now) is a coaxial two-way. No crappy MTMs here.