I put 4 AA's in a battery holder like this
Then i flipped my PSone console upside down, turned it on, and touched the negative wire to ground and the positive wire to....where its supposed to be. The psone powered on.
So I'm wondering how much power the 4 AA's have.
The batteries are arranged in series - this increases the voltage while maintaining the capacity. In your case, 1.5v AA batteries arranged in a series of 4 outputs 6 volts.
However, the capacity of AAs will not allow a Playstation to run very long. Not only do those batteries not pack a lot of power (1500 mAh, if memory serves), the voltage of batteries drops as they discharge. Rechargable AA batteries often rate better than 2000 mAh, but they usually only provide 1.2v.