My brothers father in law had an SLK320 when he retired and found it a bit flat considering the performance on paper. He replaced it with a BMW 1 Series convertible which he found to be a much better car, so much so, that when he passed, he left it to my SIL and they still have, and importantly, use it.
Depends what you want from the car, but presumably two doors over 4, and possibly convertible... If you want to thrash it every where then a manual SLK/baby BMW will be fine. Neither are perfect, but try a selection of cars before buying anything.
If you want something a bit roomier, for longer road trips/continental touring, but with some get up and go, then I would suggest a CLK500, either pre 2005 or post 2007 (the early 5.5 lump has its moments, sorted by 2007. Pre 2005 is a different engine and proven to be pretty damn reliable.
A BMW 330/335 would be a sporty alternative. As would a larger engine Boxster.
Plenty of choice around for any given budget but choose and buy carefully according to how you want to use the car... Getting this bit wrong will sour the purchase somewhat.
Some left field alternatives would include Pug 306 convertible/GTi6, 406 coupe, Merc SL, current model Fiat Spider (posh MX5 underneath), Jag XK.
All of the above are available for modest sums, obviously the bigger the budget, the more choice, and it goes without saying that if the top comes down the price goes up.
Will have a rummage for some actual suggestions...