Sound pretty tame when [FONT="]cruising although I am told it sounds immense from the outside when passing!!
I bought the Janspeed catback from [/FONT]http://www.dcperformance.co.uk/cheap/860559/landrover/janspeed-exhausts-systems/ss726.html
And the cats from
Land Rover Parts | Range Rover Spares - Accessories | Paddock (I think!

)
As Martyn said, fitting is done for not a lot of ££ at your local tyre & exhaust center. I would take on board what he said about heat protection even though I personally have not had any problems.
Hope you go for it (btw you can get top money for your old cats if you have a post 1999 model)