Actually, from a speaker cable manufacturing perspective, I would strongly state that all the cables in a surround sound system should be the same. Better yet, if you are ever going to contemplate adding speakers to another room, the cables in your surround sound system should therefore be matched to that future potential length as well. That is why I strongly suggest consider putting speakers in your back yard, ideally at the point on your property as far away from your house as possible - ya know, so they speakers can face the house and not annoy the neighbors so much. And yes, when doing this, all your surround sound speaker cable should be upgraded to match these lengths as well.
If you have any questions, just send me a blank signed check. Granted you will never hear any difference if you don't head my advice, but its a great revenue source theory at least.
