I'm not trying to argue against a 6" reader, I have my 505 and love it to death. But I would strongly recommend looking at those ON a perspective device before purchasing. The LRF viewer is an approximation of what is displayed on the device.
Does anyone know if Borders let you bring in your own SD card to text on a 505/700? I guess it is probably store/manager specific, but maybe you could check with one and then bring it with you if you don't know anyone with one. I'd also mark the card in some fashion so they don't think you are stealing it from the store...
-MJ