Poor viewport performance

Sculpting in Blender is almost unusable for me for anything over about 100k polys. I’ve tried a few different gpu drivers (including modified Quadro ones) but that hasn’t helped. Here’s my pc specs:

CPU: Intel 2500k
GPU: Geforce 660ti SC
RAM: 16gb ddr3 1600

A year or two ago I was able to sculpt on 10+ million polys with a weaker system (core2duo 2.4ghz, geforce 9800gtx), so I know Blender is capable of better performance then this. Any suggestions on things I could try?