hello
192 i/o are very good sounding converters and i do not think you would be disapointed with them
these were the ones at Capitol Recording for decades (sorry for 192 haters
if any )
but i also could read that you had quite a lot of mix farms.
In case you would like to use many tdm plugins, i would strongly suggest you to find a PE6R4-i Magma chassis.
That means you should go for a PCI X cards upgrade - The chassis will make the link for PCI E slots in the mac pro.
why PCIX instead of PCI E?
because it is still way less expensve than second hand PCIE cards.
And you can find a chassis filled with accel cards for (sometimes) less than 1000$ on ebay - usually around 1500 wich is, believe me, worth the price
Just keep in mind that there is an issue with accel cards rev G : they do not work in the following chassis mixed with other rev's : PE9R4 & PE6R4-i
so make sure you don't have one if you buy a card bundle.
Any core card rev should do, but no accel rev G
If you get a card bundle with two cores + 4 accel that's fine too. Core cards have the excat same dsp cappabilities than accels.
If i may : try to avoid process cards
Keep in mind that the PE6R4-i is just a 6 cards holder and the tdm systems can go up to 7 cards.
there is no middle chassis between 7 slots (1slot is unsusable) and 13 slots wich BTW are very hard to find.
Still with a core card + 5 accel you will have enough ressources to mix the way you want ... unless you want 6 or 7 TDM TL Spaces in True Stereo mode