Thank you all for your suggestions. Maybe I should add that I mainly do street photography and always in available light - that's why I value fast primes. However, a macro lens would also be interesting. I have to agree with John that 24/105 is a nice combination. But maybe I can afford something in between too.
I should in all honesty tell you what I use today. That is:
1) A Rolleiflex 3.5 F (my main camera - I just love it)
2) A Olympus OM-10 with 100/2.8 and 24/2.8 (these are easier to bring and sometimes better at street photography, and I tend to use these more and more)
Looking forward to more suggestions......