Pre-wired in new home.

Wire that "meets code" for in-wall use is often not audiophile quality. It depends whether the installation was a custom pro audio job or something the builder threw in to make the house more "modern". If it's the former, I don't think that a better wire from the jack to the speaker would make much of a difference for rear surrounds. Possibly, depending upon its sonic characteristics, it could be used to compensate for deficiencies in the in-wall wire though. But that's not "improving"; really, it would be more accurate to say that it is minimizing or countering deficiencies.

On the other hand, for the wire that's closest to the electronic components, a better wire would help. Cheaper wire may not be shielded very well and could pick up interference that may affect components. In that case, a better wire would help even though the in-wall wire it's connected to is not top quality.

Make sure you have good tight connectors.

Dbx,

The answer to your question will be found more in the sound that you want through your surrounds than in the wire. I remodeled my home and installed JPS Labs Super Blue 2 for five in wall surround speakers (R&L Rears, R&L Sides and a center surround). The installation also used Seas drivers so as to be voiced the same as my front speakers. I have to say that the quality of the source material that drives the surrounds from both music and video multi-channel is not that impressive.

Unless you have a well defined need for good quality surround sound I would not even think about messing with the wire that is already in your walls. The hassle of trying to run new wire will not produce a payoff that you will hear (IMHO).

Good Luck

my home came prewired. i used that wire to pull mine through the walls.