Congrats, zzboba
As a prior owner of '07 CL550 and 600 and now a very, very pleased driver of '08 CL63, would strongly advise CL63, rather than 500...
Recently did a back-to-back of CL63 vs 599 in mtn twisties w/a couple of colleagues who also own/daily-drive both 599 and CL63.....consensus favorite among these jaded amateurs for better-balanced driver's car on public mtn twisties was CL63, over the formidable 599 (safety on public roads is where 599 prob loses slight perf/fun edge over CL63)....
We're all getting CL65s in Fall, but suspect CL63 will be our overall favorite, b/c of 250lb-lighter, higher-tech NA motor and superior traction
....look fwd to seeing if 430CS proves compellingly more fun w/latest-tech tranny/diff, etc vs 599, w/a likely trade-off of less mid-range tq....
...simple solution: always have latest/greatest-tech F and MB in one's fleet: rather complementary pairing prob yielding maximal daily/wkend perf/precision/fun/safety/utility/comfort....