A lab power supply would be Ok if it can be set to 6Volts and be capable of suppling the required stall current (3Amps for 3 servos).
The bread board would work for test purposes with decent wiring , as in 20 gauge wires. Individual wires for + and - supply into the breadboard from each servo and wiring into the power supply . Check continuity of all wiring before applying the power , of course. 