If you need both ( in Logic )- your Soundcard and the Eventide you have make/build an Aggregate device. It works….but you have to make i/O Labels in Logic otherwise you get more than confused especially if you work with the I/O Instruments and Aux/Bus routing.
If you have one Adat free – use them – much easier and faster. H8000fw can´t realy route with both.( Adat & Firewire )
anyway , my setup is to work and think in 4/four Stereo Aux – because with the Main-i/O routing and the DSP A and B i/O are no more possibilties to get them independent to and out Logic with independent Signal processing. I Think .
In this case the quad 4/4 Programs are interested. Each DSP can load one of them – so you can have in logic four independent FAT Multi AUX ChannelStrips.
And you can decrease the Buffer Size in logic – otherwise you need with both Interfaces – in my Setup RME and H8000fw – a minimum of 512 Buffer.