yes, you can but what is your graphics card? if you have a GTX 780/R9 290+ Card then you are fine but depends on the quality of the PSU.
If you have a GTX 770/R9 280X or below card then yes.
What PSU is it? A poor quality 600w PSU may only deliver 500Watt and have a never stable power delivery whilst a 550 watt high quality has a much better, stable output.