jk1002: I think for TV it will be all right since it is broadcasted mostly in stereo to begin with. For DVD, speech may be a bit muddy and definilty not as clear as it would be with a center.
The speach will definitely not be muddy with Bl3!! The definition of these speakers is incredible!! With 2 beolab 3, you will get a better sound that a lot of other 3.1 systems on the market. The real difference will be in sound positionning and clarity of voice at very high volume. I always listen to my (non-B&O) TV with only the beolab 3 in stereo, and watch movies with my beamer also in stereo, and all my friends agreed to say that my stereo was way better than their 5.1. Of course a beolab 7.4 will improve the sound, but not a lot with TV, which is broadcasted in stereo, just with DVDs.
You can plug the sound output of a dvd player to the input of your stereo, and just listen what you get, that's really good. You can always buy a bl7.4 later.
My thought are only correct if you can set the BV7 center channel to "none", or set it to speaker 2 option, this was possible with the BV7 MkI and II, I hope it's still possible with the new one "bs3 based".