Thanks everyone. Preliminary result: I think I'll get a Sandisk with 8 GB. Costs one eighth of that Nokia N90, and as far as phoning and SMSing people is concerned my 30 dollar Nokia basic model does that job just fine. I know, I am every electronics marketing guru's bad dream...
Since I am hopelessly outdated as far as weight-saving technology is concerned (still carrying 2 kg of SLR camera equipment for "real" film everywhere) an extra 100 grams for an MP3 player won't matter.