Relentless are rebadged BC Racing I believe, and you have to order them via the TFSI tuning fecesbook group. Enter the playground with caution, order them, then get out again
Samuel Bryant is the contact.
Vogtland seem to get good reviews as well.
If you just want mild lowering and stiffened up a bit, consider also fixed strut kits, like Bilstein B12 Pro or VW Racing line. Everyone seems to just go for coilovers by default without really knowing what they want to achieve.