On the standard td04 turbo don't bother. will be laggy.
anything over 300 will see improvements by going front mount, There's a bit of a misconception that you can run x power on x intercooler (tmic, fmic etc), its mroe a case of use. Andy forrest ran mid 8's on a top mount which is prob 800bhp, but no way a car doing more than 1/4 mile would do it on a tmic and that power.