It is always better and usually necessary to match the sonic and tonal qualities of all channels used for proper surround sound effects. All 3,5,7,9 channels / speakers are fed the same potentioal power and nearly the same programming under some circumstances of processing selection. Find your price for the whole set, divide by the channels you want driven by your chosen system and you know your price per speaker. Stay in the same tonal line. It looks like your building Definitive Technology so you may be able to vary form factor or size but your in the brand to get them sounding right.