honestly, it sounds like you're doing the best thing ... picking up and playing with a bunch of the ereaders.
can you ask your friends if any of them have ereaders that are currently sold to see what they feel like? or go to an electronics store? i spent a lot of time in curry's (an electronic goods store) playing with their models to see how they looked and felt before i decided on my purchase. i even stopped by a B&N when i was in the states to see what the nook was like, since it wasn't yet in the uk at that point.
it sounds like you have some pretty clear ideas in your head about screen responsiveness and resolution that are best decided by your own experience of the devices.