I used to have speaker cables, untill I found a few meters of F1 PIRELLI electrical cable on the building site I was on. Man it was hard work getting the banana plugs to fit. Even through my modest setup, music sounds a bit more airier I suppose, but in no way was it a chalk and cheese difference.
Here are some vital stat's if anyone wants to know -
Electrical Resistance in metals: Silver - 1.59e-8 Ohm-meters
Copper - 1.673e-8 Ohm-meters
Gold - 2.35e-8 Ohm-meters
Nickel - 6.84e-8 Ohm-meters
Titanium - 42.0e-8 Ohm-meters
Aluminum - 2.65e-8 Ohm-meters
So you can see pure copper, like you get in electrical cables but not speaker cables (I've been told there is a reasonable Tin content in speaker cables - must find out more) is right up there with pure silver, but at a fraction of the cost. (Building site, remember?)