I've had the following exhaust setups on mein dub:

1) Extractors, unknown cat, hotdog to 2.5" straight through rear muffler. Loud, great noise on high revs, but very droney on the freeway.
2) Extractors, unknown cat, hotdog to 2.5" generic "sport" muffler. Wonderfully quiet, still great flow. Decent noise on high revs.
3) Extractors, unknown cat, full 2.25" magnaflow SS exhaust system imported from the US. Sounds freaking amazing, but droney at freeway speeds.

Very soon will be taking off the extractors and putting back on a stock mani & downpipe. I'm hoping this'll eliminate the drone. Failing that, I've got a full Remus system sitting in the shed. I'm getting too old for a noisy zorst!