Kontakt performance issues with low latency monitoring

I've upgraded from a really old i7 2Ghz laptop to a Skull Canyon i7 base 2.6GHz and has turbo up to 3.5. I added 16Gb DDR4 memory and 2 Samsung Evo 960 drives so assumed it would handle a 16 track song mainly audio with a handful of VSTs, Kontakt drums, strings and a few synths. I bought a Quantum as I thought that would give me reasonable perormance using low latency monitoring with max protection set for dropouts. I run Slate plugs on most chaels and a couple of reverbs it's all good until I select Kontakt Abbey Road drums track. The zero latency kicks in for the chael and the S1 performance meter shoots up to 100% meaning I can't easily record anything further on the track. CPU is sitting about 20% in windows and similar for S1 performance until drum track is selected. I've tried increasing buffers to 128 and still have some issues and 256 gets a little laggy. Kontakt seems a real hog in Studio One as in Ableton I can easily run 4 instances of Abbey Drums even at lower buffer settings S1 struggles with one on a small project. Anyone know of any settings in S1 or Kontakt that might improve performance or is the Skull Canyon just not great for low latency? I wasn't expecting miracles but the old laptop did fairly well with Kontakt via a usb 2.0 interface so thought this would give me a little bit more of a performance bump. I've tried various memory preload and cpu settings in Kontakt config with no success.