If you're trying to match handling characteristics after a change, you actually want to mate a shorter stem to longer bars.

Long stems make for slow steering (although they sometimes increase weight over front wheel which can make steering seem faster, depends on how much of a weight shift you experience.), and wide bars make for slow steering.

So if you go to wider bars you may want to shorten your stem a bit.

There's also the way really wide bars affect reach, but...