Matching voltages is very important, matching current ratings is only important if you are using a supply rated for less than the recommended supply. If your device says "14v @ 600mA", it needs good regulation at up to 600mA. On the supply, that 600mA rating is the maximum current draw where the supply will still deliver a well regulated volatge. You could use a supply rated at 2000 mA (2 amps) and it wouldn't make any difference. The device decides the current draw, not the power supply. If you used a 200 or 300mA supply on a device drawing 600mA there is a good chance that the voltage regulation would be poor, or you could burn out the supply.