I bought the Dual Shock 2 controllers for use on PC with a USB adapter for 2 Controllers (about 10 Euros). In all this makes me 4 joysticks with 2 double adapters: It works very well and it is much cheaper than the Dual Shock 3 controllers or PC equivalents which are of lower quality.
For those who want to do the same, I recommend buying your adapters has the same, if the configuration in the game can become tedious due to have correspondence "button -> number" different for each adapter.
