Thanks for your replies! And for bringing the SD-card option under my attention. Never thought of that, since I always used to use the internal memory only.. never needed more than 64MB of ebooks
If I read the post
that I previously linked to correctly, then updating firmware should be possible. Of course that doesn't mean it's possible for the specific upgrade that I want, which indeed may require a hardware mod.
There are plenty reports from people who have updated to whatever firmware version on the prs-500 (suggesting there are different firmware versions available). I would be interested to know where they got the firmware images from: couldn't find any myself. Any ideas?