improving bandwidth processing....dual channel afedri & sdrdx on Mac

[IQ_imbalance]

Just picked up a dual channel Afedri (yay me!) BUT i'm running into severe performance problems on my ~2015 imac (4GHz quad core i7 w/ 8Gb).  Basically i'm getting a lot of buffer overruns (underruns?) and unintelligible audio decoding  with the status display in SDRDX showing -1000 ppm.   If I turn off dual channel mode I'm still seeing -1000ppm but the audio decodes fine.   

I've tried reducing the bandwidth to 200kHz, dropping the FFT for the waterfall to 4K, and reducing the max display setting to something crazy low (5 updates/s).   In comparison I usually run my single channel afedri at 1000kHz bandwidth, with the FFT set at 16k and 50 updates/s. 

I think this is a processing issue on the computer and not a network issue as it persists whether or not i'm plugged directly into the radio w/ ethernet or not (vs. having it plugged into an unmanaged switch connected to my other radios). 

I know the dual channel radio doubles the amount of data coming in but ironically, I've been able to use the dual channel mode w/ HDSDR (controlling phasing through the Afedri control panel) on an even older (2006!) intel imac running windows, so not sure what's going on w/SDRDX on my mac.

Do i need a super duper computer w/ tons more RAM to get this to work on the mac?