Which DAC should I be using? Dragonfly RED 24-bit/96kHz or ESS Sabre 32-bit/384kHz...?

My new Yamaha A-S801 has a fancy DAC built in (so I've read), but the setup sounds like an undertaking...

I just bought an expensive AQ Golden Gate 15' Cable to connect my iMac to my Amp.  If I try setting up my new DAC from the Amp it looks like I won't be able to use that Cable anymore, as it is a USB "IN" on the back of the amp.  

Any thoughts?
If you're connecting the iMac to your A-S801 using USB, in order to use the A-S801 internal DAC, and you are connecting your speakers directly to the A-S801, then you no longer need the AudioQuest analog interconnects.
Question 1, is it my interest to use the built in Sabre DAC?  It should be better than the Dragonfly Red, correct?

Question 2, if I choose to forego the Dragonfly and Analog Interconnect, what type of high quality USB cable should I look into getting?  Or does it matter?  It MUST matter!  Right?

I need to go 12-15' to the Amp from my iMac
Yamaha A-S801's DAC = ESS SABRE ES9010K2M
Dragonfly RED's DAC = 32-bit ESS 9016

WOW does the ESS 9016 sound better than the ESS 9010?

"ESS 9016 32-Bit Like the ESS 9010, the 32-bit ESS 9016 uses a sophisticated minimum-phase digital filter to provide more naturally detailed and dynamic music, but surpasses the 9010 in overall performance"
I would suggest comparing the Yamaha and Dragonfly to determine if you prefer one over the other, or if they sound close enough that other considerations would be more important to you.