Car Stereo review would have been playing mp3s and not wavs unless they went so far as to install a beta (which wasn't publically available yet). Most mp3 encoders have high frequency roll off as part of thier design. This can be defeated at higher bit rates wtih some decoders.... If Car Stereo Review created thier own mp3s, we may never know how they did that...

The only way I could see this not being the case is if they made their messurements with the AUX in and Line Level annalogue source... but this adds another AD-DA conversion correct?