add a Schiit EITR?

More details. The Dunn J test is what Stereophile use. It is a worst case scenario. It exercises all bits and uses an LSB signal with a full output signal. 

https://www.ap.com/download/apx-j-test-jitter-measurement-utility/

If a device passes this test with flying colours then there is not much reason to be worried. Most devices do NOT pass this test well. All of the devices on Stereophile A+ list are excellent.

According to Stereophile, the jitter rejection of the Brooklyn DAC is superb (unlike their tests of Schiit products). So it should not be necessary to buy a Schiit Eitr.