Well I wasn't in the 60's but i know exactly what you mean, the Corvette's and the Mustangs all have big block V8 sounds. But to get a more mechanical and devilisih engine sound from a Mercedes, thats the ultimate fantasy!
All other sports cars have a very generic sporty sound, such as the Gallardo, various Ferrari's etc. I got overtaken at a high speed by a Vanquish, nothing special, but thats my opinion.
Ferrari V8's sound different simply because of the cylinder firing order and their high redlines compared to their 5.0L+ V8 counterparts.
AMG prefers that muscle car sound, and I think it suits them 100%.
The SLR due to I think its supercharger whine, or whatever, reminds me of an S600, with that typical "Good-natured-Mercedes" sound crossed between an SL55.
Listen for yourself...
http://www.autocarmagazine.com/popups/video.asp?AR=204422