Guys,
While the pink noise is playing, change the delay (distance) settings for the center channel. You can hear the changes in tone as you change the setting. If you can't get it exact, and your reciever has only 1 foot adjustment steps like my HK630, move the center forward or backward a few inches, then repeat the delay/pink noise test.
Also, make every effort to align the actual center with the phantom center created by the front speakers. I found that if the two "centers" do not align with each other, it will mess with the sound. I guess most would describe it as "muddy". An easy way to test the side to side location is to play music and switch from stereo to DTS, DPLII, or Logic 7 on the fly. When the imaging (particularly, the location where the lead singer's voice is coming from) stays pretty much the same, you have it right.
Pink noise contains some energy in the lower octaves that the VP series can't cover as well as the main speakers can, so the pink noise will never sound exactly the same. This is not a problem. The 2 will sound identical when playing frequencies that they can both handle equally as well.
I almost sent my VP-150 back until I found out what the heck was going on (which took hours and hours). No way will I give it up now. The center is the one speaker that guests always make positive comments about when they come over to watch movies. When we listen to stereo music, they always think the vocals coming out of it sound fantastic as well. That is until I pull the cable from the back of it to show them that the M60s are placing the singer there without any help...
