PC Specification advice for Cubase

I’m looking at upgrading my music PC and would appreciate any advice.

Here are my needs:

Windows 7 Professional or Windows 10 Professional
I work mostly in the box, using virtual instruments, sample libraries and plug-ins
I work on instrumentals of varying size
I work on cinematic pieces (via virtual instruments and sample libraries)
I need to improve upon the current PC performance I get
I need a PC that will work well with both Firewire or USB 2.0 audio interfaces
Must work well (good performance) with Cubase 9, 8 & 7.5.

I will be getting 32GB of RAM, but what I really need advice on is the motherboard / chipset and processor.

My current PC is an Intel i7-4770 (NOT the K one) on an Asus Z87-A motherboard.

However, I have run into performance problems with my current PC and Cubase.

I would appreciate any recommendations with reasons why etc.

Thank you in advance.