Tom,
If you run speaker wire from the receiver to the sub, then run speaker wire from the sub to the front L&R speakers, it won't upset the impedence seen by the receiver. If it is a surround receiver and you will be connecting a center channel and surrounds, you will need to determine how bass management will be performed.
If your receiver allows speaker configuration, you will likely need to set up the front L&R main speakers to "large" because the sub/speaker setup will be receiving the low frequency informatio too. The other speakers will need to be set to small so their low frequency information goes to the sub/front speakers.
TIC
If you run speaker wire from the receiver to the sub, then run speaker wire from the sub to the front L&R speakers, it won't upset the impedence seen by the receiver. If it is a surround receiver and you will be connecting a center channel and surrounds, you will need to determine how bass management will be performed.
If your receiver allows speaker configuration, you will likely need to set up the front L&R main speakers to "large" because the sub/speaker setup will be receiving the low frequency informatio too. The other speakers will need to be set to small so their low frequency information goes to the sub/front speakers.
TIC