Will it sound awful on idle like loud if I did this
"Nice" must be subjective as that to me sounds like the hoards of tractors which pootle up and down the lane all day here.
Of course if by "nice" you actually mean "loud" then yes, it sounds "loud".
My last car was a 2003 BMW 330d, with a nice grunty 6-pot diesel sound (coupled to a decent exhuast). It however did not need to sound like a John Deere couple to a scaffolding pipe in order to achieve the noise.
Most of the grunty throaty noise came from the induction and engine as opposed to an overly-loud exhaust.
EDIT: It sounded similar to http://www.youtube.com/watch?v=Yjle6z2z-uA&feature=related
Sound is the same
my 4 cyl petrol sounds better than your 4cyl diesel, thats a promise.