I looked in some detail for a suitable exhaust for my own car recently (1999 3.0 GTV).
Although I'm sure the Alfaholics system is great, on the basis of cost we narrowed it down to a Cybox or Longlife - Cybox was discarded because we used to have Punto 16v on a "Peco" system, which I think is pretty much the same as Cybox. Sounded fab under acceleration, but VERY boomy between 60 - 80mph (In fact, nearly undriveable!). So, we opted for Longlife, and absolutely no complaints at all. Choice of sound, choice of tailpipe, lifelong guarantee, and the quality of work was faultless. I opted for "mid sport" on a single large oval pipe, partly on the basis that it fits without cutting or altering any bodywork. I also happen to think it looks good! The normal road sound is little different to a normal GTV6, to be honest - until you floor it! But since you can choose the sound you want, I can't see this would be an issue. Cost was about £500.