Hi again mate - If you are on a budget you can start them off under the 600W but like you say make sure they are a good couple of feet from the seedlings - If you can, try rigging up 4 or 5 energy saving bulbs (CFL's) these are really cheap & you can buy them for about $1 each - they will grow quicker during the first couple of weeks under them.. then switch to your 600W. But you could start them under the 600W if you really have to - Let me know how you get on..