SUPERB. Now, detailed thoughts:
BMW GT2: OMG. HOLY AHIT. First class sound modding. That transmission, that gearbox...seriously the best sound to the real car I've heard in real life.
BMW GT3: good, amazing. Something in the transmission though I don't like, but there are so many GT3 Z4 sounds over the years that this could be one among many :)
Ferrari FXX: tied with GT2 on best sound
Zonda R: GREATLY improved since last version, no volume issues, clearer cockpit sounds, totally immersive.
McLaren F1: what can I say? BMW V12, good and the best new mod in the pack. The externals are particularly good on this one!
Nissan: I thought the original couldn't get better but it did. However, it feels a little dull, not in sound but energy. The real car is so dynamic, this feels a little lackluster, gutless. But the actual sound is very close to the real car :)
Lotus: BEST NON-GT CAR SOUND EVER.
I could go on but you get the point. Mercedes was the only one where the internals did not impress me, there's a strange noise in the background at 5800 rpms. I still use the older sound you made. But as far as immersion, realism...my favorite sound used to be the Camero GT3, but these are a whole new level of real. Finest sound modding in AC to date. Forza Fonsy!!!!