I don't think the internal hard drive size makes any difference really. While the games do save part of the content onto the HD, most is read from the discs. Also chances are you won't hold onto old games, they will get traded in so you will delete the old content too.
You can put movies, pictures etc onto the HD to watch them, however you can also plug in a USB drive into a PS3, so if you do run short on storage you can pick up an external drive
As for good deals, have a look at the usual suspects, the PS3 price is set my sony so you can only get a deal in a bundle