Looking to replace my 4,1 Mac Pro with a 2013 Trash Can - Some Questions...

[JoeM]

Hi All,
I'm currently running PT 11.3.2 with a PT Native PCIe card and an HD Omni interface on an older 2009 4,1 Nehalem 2 x 2.26 GHz Quad-Core, 32 GB RAM along with a UAD Quad PCIe card for my UAD plugins and a MOTU midi express 128 for my MIDI gear. I'm on OS 10.10.5 Yosemite and everything is solid and working great.

I'm starting to run into issues with 3rd party plugins needing a newer OS and after seeing the price of the upcoming 7,1 Mac Pro, am thinking I might pick up a 2013 3.5 GHz 6 Core trash can with 48 GB RAM to get me by for the next few years. PT 11.3.2 is fine for the way I work and my recording needs so I don't need to go to PT Ultimate. If I had to upgrade PT at some point, I'd probably look for either PT 12, 2018 or maybe 2019

With the above in mind, I'd like to ask these questions:
1. Knowing my UAD Quad card won't work with the trash can, I'll probably sell it and buy an Octo satellite. That would leave me with only the PT Native PCIe card needing a home in a PCIe extension chassis. I'm thinking of looking for either a used OWC Helios chassis or getting a Sonnet Echo Express SEII chassis, both being PCIe 2.

My question: does anyone have thoughts on or experience with either of these two external PCIe chassis?

2. With the trash can, would Sierra or High Sierra allow PT 11.3.2 to run or do I need to update PT to use a trash can?

3. Regarding a needed video card for smooth meter performance, could I use the AMD FirePro D300 x 2 with 2 GB RAM or do I need to get an AMD FireProD500 x2 with 3GB RAM?

Thanks in advance for your help,

JoeM