I am generally happy with my DAW`s performance, the weak link(?) being i7 gen. 3 processor (Ivy Bridge). What, if anything, makes the latest iterations of i7 better? (6 & 7) . Like I said, I am not having any issues per se,  I just gots to know! I would probably have to go with a new MOBO to accomodate any upgrade, right?

I think I would wait for Intel to bake the permanent fixes for the Meltdown and Spectre vulnerabilities into their next generation silicon.
 
Any CPUs that you buy this year will still have to use the microcode and BIOS workarounds for this flaw that are potentially performance degrading.  If you don't absolutely need to upgrade right now, in my opinion it would be better to wait.

The latest Gen i7 8086k provides six cores (12 processing threads) at 5GHz.
That's more cores, faster clock-speed, and the CPU is faster at a given clock-speed.
In short, it would be a significant upgrade.
 
I wouldn't worry about Meltdown/Spectre.
We've got professional composers pulling 4000+ voices of disk-streaming polyphony from a single machine.
The performance hit is "minimal to nothing" for most single-machine users.