I don't remember, what kind of output does the PS2 have?
Two RCA (white and red)
An optical out
Anything else?
If there's nothing else, it's going to be expensive to get true 5.1 out of the PS2.
The PSU will only output stereo through the RCA jacks. On a set of speakers like your x-530s, you're not going to be able to enable anything with them that will expand a stereo signal to all your speakers.
You can easily get sound from them, but it will only come out of the front left, front right, and sub.
This RCA to 1/8" adapter would plug into the output of the PS2 and allow you to plug in your green connector of the x-530s. The center and surrounds wont play anything, but it's a start.
Do you have a soundcard or integrated audio?
If you have a soundcard (or nice integrated audio I guess), it's possible that you could have a setting that would expand a stereo signal to play on all your speakers. It's not going to be true 5.1, but it would then play on all your speakers. You'd accomplish this by pluggin the PS2 with that adapter (and an extension cable probably) into the line-in of your soundcard. There may be a setting in your sound utility program that would expand this to all the speakers.
Ok, the real solution to this problem is to get a decoder that will output to 1/8" jacks.
This creative decoder would do that, but I think it would be a pretty foolish idea to hook up a $120 decoder to a set of $40 speakers.
With the decoder option, you'd get true DD surround from DVDs (and games too if the PS2 outputs an AC3 stream somehow in gaming, I don't have one so I don't know).
If you like the true surround idea, I think it would be a better idea to just get a
set of speakers with a decoder built in like these z-680s. It's not that much more than getting a decoder alone, and you're getting much better speakers than the x-530s are.