Quads are a rare set up and you are limit to what rear options you can have. For te Ed30/normal GTI rear you are limited to cutting you own bumper.
Me and Robin on here have the quad set up, Robin used to have an ABT rear lower bumper with quad cut outs fitted but has since moved onto the r32 rear with an Osir carbon fibre exhaust trim with custom quad from Milltek sporting ceramic (I think) coated tips. I have the same set up but with a matte carbon exhaust trim and normal Milltek quads.
The R32 rear with an insert is the easiest way to go but the lower rear bumper is ~£200 second hand with reflectors etc, then have that sprayed, then an insert from Osir ($500+) or SRS-tec (€169), then the exhuast which Milltek don't stock anymore and I'm not sure if anyone else makes them off the shelf so it'll have to be 2nd hand or a custom made exhuast.
There are other rear option with different lower bumpers from ABT, SRS-tec, other big tuning companies and ghastly eBay stuff, which will all need painting etc.
It is worth doing but is expensive, I'll try and dig out some links in a little while and one to Robins old build thread that shows the different exhausts and bumpers he had, which will help as his is tornado red.
