I personally researched (to death) all the 6-pot and 4-pot options, including the 18z.
In the end I picked up a pair of mk7 GTI PP/Clubsport calipers (same as mk7 R/8v S3) which admittedly won't have quite the stopping power of the 18z or TTRS caliper, but the discs are light, pads are cheap, and I won't need spacers.
Time will tell whether they're enough for my intended 350bhp. If not, it's back to the drawing board.
imho I can tell you that oem brakes aren't up to the job when it comes to upping the hp unless they're rs or ttrs ones and I know that from personal experience so thinking I may as well go big as I'll need to be stopping quick if I want to go forward.
Fair play mate, I guess I should be doing the same, but for me there's always a bit of the 'brake porn' factor involved in the 4/6pot kits. It's the law of diminishing returns. I should hopefully have the whole kit on and working for about 500 quid. The cost of the bigger stuff all adds up, before it's even fitted.
My main aim is to avoid debilitating fade, rather than have something that puts me through the windscreen. I think I got to the point where I asked myself how far I really needed to go with it. Would spending another 500 quid get me twice the performance.
Anyway, we'll see. I might end up going for a bigger kit at some point if these don't cut it. But I thought it'd be interesting to see how well they cope, they're still a bit niche. If I've got it right, the piston diameter on these is 3mm bigger than the usual S3/R32 caliper. Could be good, might be crap!