The white foam base of the Way Excellent II Turntable Mat is extemely efficient at damping platter resonance. A Way Excellent II Turntable Mat of sufficient thickness (3.7mm or more) will thoroughly decouple and isolate the record from a resonant metal platter.
A dBNeutralizer mat with grungebuster mat on top would not necessarily be overkill, and the result with some tables would be very good; with most tables though, it wouldn't be as good or better than a Way Excellent II, and would add a lot of weight to the platter.
Steve
Herbie's Audio Lab