all models need S4 bumper shocks. You can modify stock ones too if you dont have the proper ones, by adding a spacer on top.
The S4 uses the simpler pre-facelift sidemount brackets. If you have a facelift car, you need to remove the facelift sidemount brackets and fit prefacelift ones. You also need to move one of the little bungs to accommodate this.
I think the side mounts are quite cheap, it's the bumper shocks that are expensive to buy new. Keep a look out and some will turn up cheap I paid £35 delivered for the shocks. As a temporary measure I used a pair of 21mm sockets as spacers on top of the original mountings and made the longer bolts with threaded bar and two nuts locked together.
I had a pair of supports for sale for 2 months for £30 over on srs ... eventually sold. Not what you want to hear, but, they are about. Try stevieyid on srs ... a prolific s/rs breaker. May probably be the odd breaker coming up on there soon too. They dont seem to be selling "whole" atm
I had to put 2 front bumpers on my S4, high kerbs are a *******. If you've got the PFL side brackets it's all good, then all you need is the shocks and mounting bolts as they're different too