I considered a few different Mercedes. CLK55/500 , SLK55, E55/500 etc... Also, Looked at a local 54 plate S500 few months back, Didn't get to drive it. But from what i saw I didn't like it all that much tbh. Was missing quite a few options as well. Couldn't see it handling all that well either. Then again depends what you want it for.
The 2008 w219 CLS500 i went for in the end was originally a ex-mercedes managers car where he changed car every 4 months so naturally had the top spec of whatever he got. Otherwise no doubt it would have been the usual poorly specified CLS model. Napa leather Massage + ventilated / heated / dynamic seats, inbuilt digital TV / DVD player, Keyless Go, Steering paddles etc.. Are some of the options on it that aren't usually ticked when new.
Loved the w211 E55 AMG i test drove awhile ago, Sadly it had a hard live and was a wreck even so it still went well. Those are one of the best engines Mercedes made around that time the M113 / m113k. But they are too hard to find in good condition for a reasonable price.
I'd recommend you just go and see / test a few different models. E class, CLS, S class etc.. See what suits you. But as DG said do your research on them before purchasing. Quite a few bad apples / ticking time bombs out there best avoided.. Specific years / engines etc...