How hot is your sub and what does your house curve on your bass look like? You may have so much deep bass that you don't hear/feel the mid/upper bass slam frequencies that are a bit higher in frequency, and which are more likely to benefit in the near-field. You might have to back off on the house curve and/or overall level to actually hear the higher stuff too. Only listen at -15? Assuming you are calibrated to theatrical ref level, that's pretty whimpy, without the subs hot, especially for movies. Some good mains, properly configured (no Audyssey) ought to sound pretty nice at -5 on movies, or even higher depending on the mix. There's plenty of bass to be felt that's above the sub range, but not really with whimpy mains at only "-15".