I think it would work just fine. I'm pretty sure when you go "preamp in" on the Mackie it bypasses the graphic EQs, which is good. Hopefully the master volume still works so start with that turned ALL the way down. Play some music through it and SLOWLY turn it up. Remember, NS-10s aren't supposed to be screaming loud. NS-10s can handle 60W (program) and I think 100W (peak) at 8 ohms. Rule of thumb is you should use a power amp that is 150% to 200% HIGHER than what the speaker is designed to handle before distorting. That way you never push the amp into clipping territory and send square waves to the speakers, which can be very damaging. Mackie claims that 808S puts out 300W per channel at 8 ohms. It might be less than that because they tend to exaggerate. That's more than you need for the NS-10s but if you keep the master down low it should be fine.
"The importance of reproduced sound lies not in any inherent acoustical value, but in what it signifies to the soul of the listener." - Bruce Swedien