i think you should start at your own side and stop thinking what reader can do what. so try to figure out what size it should have, which formats you like or need etc. personally, i started of with the Sony PRS505. great device, absolutely. even my wife was reading with it. after a couple of month i found the screen a bit to small. now we've got both a Irex DR800SG and i can tell you..... smashing. what a super device is that.
what i'm trying to say; it all comes down on what you wanna do.