I'm not sure what you mean by all of them have to be the same speaker. If you're talking about a system (epic, etc.), then that might be the case. I think that the discount is the same anyway (I could be wrong, but the systems are just compilations - minus 5%). If you buy more than 5 pieces, then you get 5% off...
So, if you were to delve into the outlet, get some fronts, center and surrounds and a sub, no one would be stopping you from mix-matching colors - and you'd get the 5% package discount and the 10% outlet discount. That's what I did.
