CPU Spikes (Pops & Clicks) - iMac & 11.3.2

Hello all,

I'm looking for ideas for how to address the pops & clicks I get when using Pro Tools 11.3.2 on my new iMac. It happens when (1) using multiple (12+) instances of virtual instruments (esp Play) and (2) with "Ignore Errors During Playback" checked. Left unchecked I get the CPU/Buffer Size error. Below are specs and a list of things I've already done/tried:

Specs:

27" Retina iMac 4.0GHZ i7, 16GB RAM, split Fusion drive. (Yes. Yes, I know. I know.).

Yosemite 10.10.5

Pro Tools (vanilla) 11.3.2. (;))

Cache at 1024 Samples.

System Drive: internal 128GB SSD
Samples Drive: internal 3TB drive (7200RPM)
Sessions Drive: external 3TB Lacie Thunderbolt
Interface: Komplete Audio 6

During playback of a session with 15 instances of Play & about 6 instances of Kontakt, plus one or two stock EQs, RAM usage is at about 50%. Across the cores usage rarely gets above 14% but overall CPU meter will spike and throw an error.

Stuff I've Tried:

- Downgrading to Mavericks (no joy, iMac came w/Yosemite)
- Split Samples drives
- Avid's optimization steps (WiFi off, Energy Saver stuff, etc etc)
- Clean-installed Yosemite. Re-installed Pro Tools. Trashed prefs.
- Bouncing tracks (which, of course, works, but is a PITA)
- Unloading unused articulations in Play; purging samples in Kontakt

Stuff I May Try:

- Splitting the Samples drive again (to new Thunderbolt and/or $$D)
- Re-downloading a couple Play libraries in case I have corrupted samples
- Buying more RAM (always on the table :D)
- Upgrade to Pro Tools 12
- Switch to PreSonus Studio One 3 Professional
- I work with multiple single-instrument instances of Play rather than one instance with multiple instruments so as to spread the load across all 8 cores. I could change this method too.
- Buy a new damn computer

Stuff Already Suggested:

- Vienna Instruments Pro
- Buy a Mac Mini or two and spread out processing power

Thanks in advance!
Laura