Rich, it's just about impossible to screw up regular lampcord type speaker wire. Capacitance is pretty much of no significance for speaker wire(it is for interconnects); a very high capacitance could make some poorly-designed amplifiers unstable. Excessive inductance in speaker wire would roll off the treble response, but inductance is governed primarily by the distance between the centers of the two conductors in the wire, and the usual closely-spaced wires have low enough inductance that the small differences between them at 20KHz aren't of audible significance.
Now if those "doo-dads" that you mention are magic boxes attached to the wire which intentionally add excessive inductance, then there could be created a roll-off of the highest frequencies which might be audible. If so, that wire might be praised as "smoother, sweeter, less harsh", etc. although it would actually be reducing the fidelity of the sound. If a recording really needed that treatment, that's what tone controls are for.
