[issybird]

Older devices have two significant problems: the battery's likely shot and the resolution isn't as good as it is on current devices (even more important when there's no front light). Oh, and a third drawback: they're slow.

My advice would be to get the current Kindle Paperwhite and turn the light off. It's $10 over your maximum, but eventually there will be a sale. Maybe even for Black Friday, although that might be a little premature given that it's just come out. The Paperwhite is 7" with lickety-split page turns.