Maybe JeMCG talk about the enveloping sound field + decibel pressure ( I don't know the right word for it ) I often listen to trance music, at low volume 40dB, it lacks punch, sounds flat and lifeless, but pump the volume to 60dB or more, then we are talking business here, punchy mid and shaking low, fuller high, the sound felt alive and "powerful".
I've watched live racing through my AVR a couple of times, the sounds from higher decibel does make it a lot better than the tiny tv speakers

, but I won't crank it up all the time, I love my hearing better
In GT5 case, the sound source is not that "sexy" compared to other games like Forza or NFS MW, I guess PD needs to have a middle ground here, realistic but also engaging.