I have a relatively high end speaker setup (Focal Chora bookshelves and a Rotel stereo receiver all connected to the PC and AppleTV via optical cable) and I suffer from the muffled dialogue situation. I end up with subtitles, and I thought I was going deaf.
I strongly recommend you try adding a center channel to your viewing setup, also a subwoofer if you have the space. I had issues with clarity until I did that.
