Honestly, the perfect position, MRC and various listening modes. I would try certain speaker spacing (toe in, toe out, no toe in, etc), center channel above my TV and for example Trifield for a couple of months and then would try something else. Then I got some acoustic panels, tried other speaker positions and MRC for a couple of months.
I finally found the perfect position for me with [very] slight toe in (about 6ft apart between L&R), elevated center (about 8 inches from the floor and 30 degrees pointing upwards) and I listen to music in pure Direct mode. For me, this provide the best imaging I had ever heard (EVER). The other thing I noticed, is when listening to other modes that involve the center channel, the settings (depth, width, level, etc) for the center channel were left unchanged (i.e., at zero).
I've had this setup in place now for several months and I have no desire to change it. I initially got caught up in a tweaker's fantasy with MRC for the first few months and then I realized correct placement and acoustic panels make a far greater impact then MRC. While MRC is powerful tool, I've had better success with simpler (but time consuming) means.
Nick