EAR pre a good match for active ATCs?

Is an EAR preamp (864 or 868) a good match for active ATCs? The EAR's output impedance is 600 ohm and the ATC's input impedance is 10k ohm. Based on the minimum ratio of 20 and above, the bass might roll off on this pairing. Would it still be optimum?
had this combination - 864 with ATC 20A. very good, the best active pre i've heard with ATC and i've heard many. later i went down passive preamps route which sounded better to me but i can alwyas recommend 864. i have no experience with 868 but i don't think it's very different.