Swap i7 3770K for i5 IMac?

Hi all, i have had problems with Cubase ever since the version 8 release. Basically vst meter is way higher than it ever was before. Steinberg have been disgraceful and showed little or no interest in helping my fix the issue.
I now find myself considering an Imac as I am now getting a lot of crashes since introducing Komplete Kontrol.

My specs should be at the bottom of this post for my pc, but basically I have a chance to swap the following

i7 3770K Asus MB
WIndows 10
GTX960 4GB
mouse keys etc

Imac i5 sandy bridge
27" screen
12gb ram
not sure which IOS this is but has dual boot to windows 10 also.

I mainly run VSTi using Omnisphere 2, N.I. Komplete ultimate, Steinberg Halion and other VST and Korg legacy.
Basic template I am setting up has 6 drum tracks vsti, 16 N.I tracks (komplete kontrol), 8 omnisphere tracks, 8 steinberg tracks, 8 korg tracks, 8 audio instrument tracks and 16 vocal tracks.

Can I run another monitor from the i5 and will the i5 CPU cope with the workload any better than the i7?

I would normally think an i7 would out perform the i5 handsdown but Apple seem to be able to get the very best from hardware using there OS.

Are there any pitfalls with IOS compared to PC?

and help appreciated.