I'd go with after market to be safe. They're made to be that low. Either koni yellow or eibach pro dampers. If you already have h&r though I'd stick with their struts as well.
Just curious, I'm looking to lower my car soon on H&R race springs. Simple setup for now. Well I noticed a few people selling different struts like S6 struts and RS6 struts.. What is the difference? Would I be able to install them on my struts or is aftermarket manditory for a safety feature?
Low and slow rollin oem fresh
Factory sport struts (including the S6, don't know about the RS) only ride an inch or so lower than stock, and they do that by moving the spring platform. Afaik the H&Rs tend to sit pretty low so they'll probably bottom out the stock struts and kill them fairly quickly. I'd go with aftermarket ones that are designed for lower ride height like the Bilstein B8s
Throw an Audi engineer down a hole with a ladder and he will fashion a shovel from it and tunnel his way out