Many thanks for all these kind responses.
We plan a backpacking trip through the country, and therefore it would include visits to cities, towns and sites but also a couple of treks as well.
Basing on my experience and knowledge of the extremely high transaction fees entailed in any withdrawal of money from ATMs abroad as well as purchases with the credit card, I know that at least in the case of my Israeli home credit company it is simply too expensive. This is why I even prefer changing cash twice - from Shekel to Euro and then to Krona.
But your advice is indeed very helpful. I will challenge myself (though not too much) to see if I can find a place in Munich that changes into Krona (given the exchange rates on the links you mentioned), but I'd also be glad to know where can I expect the best exchange rate in Reykjavik.
Again, thanks a lot!