I dont use a mod, have dropped 4 roe deer one after the other in the same field and have shot more than one fox in a field. I dont see the advantage of the extra 200 quid +, i think you would be better putting that money into a better scope.
The only advantage i see is for your hearing, for noise reduction in a built up area and so when lamping it is easier to identify you hitting your quarry.
If you have money to burn then fair enough, if you dont it can be spent more wisely.
FTB