Hey Matt. Thanks for the update.
I've done a little research into this and had a good think about it - though it's a great buy, it may not be quiet enough for me (underground garage - I'm already setting off alarms with my Drager!)... at this price, I'm very tempted to buy it and sell it on if it doesn't tick the right boxes.
So in short, thank you but I'm going to prioritise other more pressing things on the car for now.
For anyone that's interested, this is the special edition of the HKS Hi Power - full stainless piping, with a titanium exit and the benefits of good ground clearance. Buy it before I change my mind...