#1 the power supply depends on the type of driver as well as the motor. Settle on the driver first, then read here to pick the supply:
#2 All of those look workable. The L298 drivers are expensive but appear to be providing active current regulation. This allows lower power supply voltage while still proving higher top speed. The mosfet drivers are much less expensive (easier to repair if you fry one) but don't appear to be actively regulating the current through the coil. You will need more supply voltage to get higher speed and then motor heating will be a problem. None of them provide microstepping except by PWM from the PIC. You might want to consider the Linistepper design:
techref.massmind.org/techref/io/stepper/linistep/index.htm although it is not really intended for 3 amp motors, it can run them in full or half step and uses less expensive (easy to replace) drivers but still provides active current regulation and microstepping (at lower currents). Open source... board layouts, firmware, etc... all available in addition to very cost effective kits.