I want the best speed possible, but if the PS3 is just built for Cat5e, it doesn't matter right? I am uninformed but I want to use the best cable the PS3 takes advantage of.
Both cat5e and cat6 are rated for Gb Ethernet. Cat6 will perform better in certain situations, but in this case you won't notice a difference. 5e is fine.
So Cat7 is completely unnecessary?
@gbastasch: I haven't even seen a cat7 cable in the wild yet so seems pretty incredibly unnecessary. Cat6 is only marginally more expensive then cat5e and does have better signal quality and strength so go for it.
In what situation would you need anything better than 5e for your Playstation? Are you trying to run an ethernet cable 100 meters through a maze of microwaves and fluorescent lighting ballasts?
Edit: Actually to answer your question, the different Categories of ethernet just set standards for what the minimum specs should be on the cable. So you could put a Cat7 in there, but you won't see any speed difference unless we're talking tons and tons of interference from other devices.