I agree, but the fundamental problem lies with the original sample/recording or lack of. So yes all cars sound better due to a wider sound field created by multiple speakers of a better quality.
An example would be to compare a very low bitrate MP3 song versus the Lossless FLAC version. FLAC will always sound better. Play the same MP3 or FLAC song through say the loud speaker of your Mobile phone and both will sound bad, perhaps with the FLAC sample not being very distinguishable from the MP3 version as the Mobile phone speaker may not be good enough to show some or all of the quality of the FLAC sample. Play both samples through a Dedicated 5.1 system, and both will sound much better of course, with the FLAC sample being able to really shine.
The above example is based on 2 recordings of a song that is an authentic representation of the actual song it was recorded from. The issue with GT5P is that many of the samples are incorrect, and not representative of the actual car, with some sounding unlike cars all together. Some of the cars that PD seemed to bother with, do in fact sound good, and what we would expect a car to sound like. Whether they are accurate to the actual car I am not sure.
Some of the cars I think actually sound like cars are the below whether true to the real car it represents or not, either way they sound like cars. IMO:tup:
Type R
Tuned Clio
BNR Skyline
Skyline
There are a few more, but those spring to mind.
To enjoy GT5 for all its worth, and in this case its sound, should require no less than standard speakers, for a richer experience, than a 5.1 set up is the way to go. I have both and I am not happy with GT5P regarding engine/exhaust sound.
Forza 3 as discussed many times here,despite its poor sound engine, and lack of sound changes to reflect driving views, as well as poor replay sound; all areas that GT5P are more accomplished at....The actual bare bones samples/recordings of the exhaust notes are overall a better representative of the cars they are supposed to mimic. Forza 3 sounds good through TV speakers and better through a 5.1, just Like GT5P, but the base/level started from if just considering the actual samples and not the 'sound engine' than GT5P is lagging behind.
Its no good doing clever things through advanced sound engine if you are working from mostly poor/incorrect samples, and that is what PD have been doing way too much of IMO
As I have said prior in this thread, we will get a larger pecentage of cars in GT5 sounding better versus all previous releases, with perhaps further improvements coming via patches, but on launch don't expect all 1000+ cars to be 100% true to life, perhaps our best hope is that all of the Premiums will sound like they should.👍
always funny 
Sadly no game this generation will have sound that good.*
