Thanks for all the informations, guys!
A Kindle DX is out because I can't play with a demo version at all, whereas I'm able to play with demo versions of the Kobo Touch and and Kindle Touch (as well as the K4, KK, Kobo non-touch, iRiver Story HD and Sony PRS-T1 - but none of those float my boat!).
I have one more question. I've gone and had a play with the Kindle Touch now, and I noticed that the menu screen is text-only. I played around with the settings, but couldn't see anywhere to change that. Is there a setting in the non-demo firmware to allow you to display book covers in your home screen as a default (or, failing that, any software for the jail broken Kindle Touch)?
It's so hard to choose between them!