seedlings Light ?

I have recently just germinated my seeds and i am ready to put them into some root riot cubes,,,

would my 600w Dimmable HPS be too much for them or not i can put it to 250w 300w 600w 650w ?

tent size is 4x4

I put mine straight under my 400 and they seem to do fine. If you dim it and gradually turn it up they should be fine