So you have a decent GPU and a CPU that does hyper-threading at 2.66GHz. Try this script. It has decent picture quality, great smoothness but don't really know about the CPU usage. Please try it out.
svp_flow_lib="C:\\Program Files (x86)\\Avisynth 2.5\\plugins\\libflowgpu.dll"
V = ffdshow_source()
S = V.MSuper(pel=2, hpad=16, vpad=16, rfilter=4)
A = S.MAnalyse(isb=true, blksize=16, overlap=4, plevel=0, pelsearch=3, search=3, searchparam=4, lambda=2000, lsad=1600)
B = S.MAnalyse(isb=false, blksize=16, overlap=4, plevel=0, pelsearch=3, search=3, searchparam=4, lambda=2000, lsad=1600)
V.MSmoothFps(S, A, B, num=FramerateNumerator(V)*5, den=FramerateDenominator(V)*2, algo=23, sadgamma=2, sadml=200, ml=0, blend=false)
GetMTMode(false) > 0 ? distributor() : last
This script is for 23.976/24fps videos only as I assume that is what you watch. If you have videos of other framerates please let me know.