These chaps are helpful Alfaholics: Stainless Steel Sports Exhausts and I think their system is highly rated. They also have a review on their website.

You can buy the sections separately, which is handy.

I have the transverse silencer taken out and it sounds lovely, if a bit boomy. The Alfaholics guy's leave the trans silencer in and replace the rest with free flow cat/silencers.

I was wondering whether to take the middle silencer out and replace it with the alfaholics middle section (free flow silencer ) but I think it'll make it too loud, so am leaving it. They are very helpful and said for power + sound that their cat replacement section is better than replacing the middle silencer.....