increase current of a microcontroller output
There appear to be two things going on here:

You need to be able to switch the full current the motors require.  A simple way to do that is with a FET low side switch:



This particular FET can be driven directly from a PIC pin without any additional parts.

Note the reverse diode across the motor.  This is not optional.

Your power supply can't supply the full motor current.  You mention that the micro gets reset when you do get the motor to move a little.  If the power supply can hold up the voltage, then this shouldn't be happening.  Try to run just the motor off the power supply directly, and watch its voltage.  If it goes down, then you need to get a beefier power supply.

Other possible causes of resetting are that you omitted the reverse diode across the motor (D1 in the example above), omitted the bypass cap across the Vdd/Vss pins of the micro, MCLR is not properly held high, or the PGM pin is floating and LVP is not disabled (the default).  Make sure that ALL power and ground pins are connected, including AVdd.  And each power pin gets its own 100 nF to 1 &micro;F ceramic cap close to the chip back to the nearest ground pin.