maybe useful to split sounds up into:
induction - filter/s, compressor/s, bov/s, throttle/s, plenum
exhaust - manifold design, turbine/s, wastegate/s, cat, muffler
engine - I am no expert but from above lifters, capacity???? RB20, RB25, RB26, RB30
induction/exhaust noises may more depend just on the turbo system bolt on design (ie single, twin, big, small) and the exhaust gas potential of the engine
what do the N/A versions of these engines sound like with an exhaust, say an rb25de - are they almost louder because the turbo doesnt 'muffle' the exhaust note??