Just a minor correction in terms, not likely RF (radio frequency) noise that you are experiencing but "inductive" noise. The motor and associated driving circuits create fields of magnetism that affect nearby circuits, propogating through wires in many cases, or even the traces on the boards. The problem is the noise gets in way early in the audio stream. Everything mixing and amplifying downstream is going to aggravate it, and it can be very difficult to remove the root cause.
I spent a lot of time on my DE Maverick, and what helped the most was floating the sound board. It's the only game I have had this actually reduce the noise on. Floating the ground is somewhat counter intuitive to my nature, but I work in pro audio stuff so I am familiar with ground loop problems so I gave it a try. This is part of the reason why our pro audio products are often designed with highly isolated digital and analog grounds.