when you are looking at the PS3, they have different gb. i know my son has a 60gb which will play the games from PS2. there are others ones which wont play the older games. I cant tell you much more info but them but i know there is different versions.
I found the 120 GB version with Call of Duty MW2 for €299.99 from GameStop was the best deal I could find. It helped that this was the game that was asked for as well!
Managed to get €130 off the price by asking the kids if there were any games lying around the house that were not being used, so traded them in.