Maybe worth even giving Hayward & Scott a ring .....
http://www.haywardandscott.com/results.asp?category=13
then you could get a 3" Votex rear box (as i know you like the noise),
http://www.scoobyworld.co.uk/catalog...oducts_id=1375 , a Hayward & Scott 3" downpipe and see if they would do something with a centre section to link the two up.