My setup now is a Squadra tuning chip (+30bhp +60nM), original downpipe, Alfaholics sports-cat, Alfaholics centre-silencer and original TB (single pot) rear silencer.
When I bought the car, all was original except for a Raggazon open-pipe centre silencer, noise for me was a love/hate burble at tick-over. It was just a bit too loud some days and other days I was fine with it. As soon as you get >2000rpm, the turbo takes up a lot of noise so no issues noise-wise on the motorway. On that same 1-10 noise scale: tick-over 7, motorway 4
Next I bought that sports-cat, burble at tick-over was louder and things started to rattle in my interiour. Tick-over 8, motorway 4
...so bought the Ragazzon mini-centre silencer. Made the car as loud as I bought it, tick-over 7, motorway 4.
Last October that love/hate at tick-over was sligthly more on the
-side so bought the Alfaholics centre silencer. I'm not sure if that is any louder than an original centre silencer, but price-wise it was awfully close to an original (and stainless). But it did do the trick for me. Tick-over 5, motorway 3
So for me with the current setup, I think the car now sings instead of shouts, so I'm not changing anything anymore
But as can be read on any car-forum; exhaust-tone/noise is very personal so you might like a bit more noise.