The original (R170) is not galvanised, the second generation (R171) which I believe is 2004 onwards is - so tin worm is less of a problem, although rear sub frames can be.
If you contemplate a V6 petrol (eg, SLK280) research on here and MBOA, early engines had potential major problems.
For roof down motoring and leather interior, heated seats and airscarf are good options, memory package would also be nice if both of you will be driving it.
Plenty of choice of SLK200's (1.8l petrol), often ladies cars, I believe they are "adequately quick", but the only SLK I've driven is my 280, and as it's my car I would not even look at anything under 3L, and was barred from looking at the 55AMG I'd really have liked!