I've read a few articles (Thiel's site) that stated if your front speakers image well and are placed correctly then adding a center speaker can actually degrade the multichannel experience.
I have 2 great imaging speakers and will have to spend a considerable amount to add a matching center speaker and now wonder if its necessary. I'm happy with my current 4.1 setup, but always assumed the center will add to the whole setup.

Any opinions?