In my opinion, what benefits you would receive are dependant upon many factors like which Mackie you are using, what mics you are using, how you are micing the drums and in what sort of room and even what type of drumset you are using and how it is set up (heads and tuning). After that, you have to ask ask yourself how you value the change in sound and what you are capable of doing with it come mixdown as well. Not to mention what preamps you would be upgrading to. Personally I find a huge difference between recording drums with API on the front end as compared to a Mackie. I am in a different situation though with what clients expect and what my system is capable of doing (i.e. how accurately the differences can be reproduced to allow me to do my work). There is a good chance that the improvement, especially on drums, may not be very large due to the factors listed above, especially if you purchased 8 channels for under $1000.
