I installed a Supersprint on the same car (97 2.8). It has a mellow tone at idle, but a rich wail at WOT. The unit is a stainless steel catback with typically impeccable Italian craftsmanship. I have had mine for going on nine years and it still looks great. My only concern is that the outlet pipes are a very tight fit within the stock cutout in the rear bumper; probably less than 2mm clearance on each side. The pipes are double rolled so they don't get really hot, and I have had no issues with any melting of the bumper plastic. Just make sure that you install yours well so there is no contact.
I can't say the unit (or really any other exhaust) provided any power advantage, but it is probably half the weight of the stock unit so there is a minor performance advantage there