If these were not changed on the router you wouldn't need to change them for the PS3. I would say the problem is definitely in the PS3's wifi card not picking up enough signal.
At that distance you could easily go with a wired connection- you could run the cable underneath the floor so that it isn't visible. This would be cheaper than going with a range extender and give you an ensured connection to the internet. The Linksys WRE54G, for example, is $99.99 at Best Buy. 30 feet of ethernet cable should only be $35 or so.