It's not the fact that's its an additional right and left channel. You could add more right and left channels to your front stage and enhance the front stage. The problem is the fact that its behind you. Don't get me wrong, because you have rear fill does not mean it won't sound good. The thing is if you want concert type sound rear fill will negatively effect it. An example would be if you were at an actual concert and the artist are playing on stage but one of them(say the guitarist) is behind you(which of course would never happen) it will draw away from the sound on the concert stage. Another way you can test what I'm saying is fade your sound to the rear and you will notice how it takes away from the sound in the front and makes it seem like the sound is coming from behind you. That's why it's always important to have porportional power going to your woofer and front stage so one doesn't drown out the other. You want it to blend. Now if you dont' have a woofer then I would definitely say you should go with speakers in the rear. Also if you're going for surround sound. That's the design of surround because it will make you feel like you're in the movie. Sounds coming from everywhere. I'm not really a technical type person, my knowledge is usually in a laymans terms format, but I hope I explained this pretty well. One last thing you said you like to be immersed in sound well if done properly you wouldn't need rear speakers to fill immersed in sound. Bass by nature is a sound that blended in you can't really tell where it's coming from. So with the right power to the woofer and the front stage you will feel immersed, as long as you're in the front seats.