squares of what? soil, rock wool or what not. soil as long as you can move them without crushing the roots much i'd move'um, if its rock wool wait until you see a decent amount of roots starting to grow out of the wool.
as for the 600w id wait a few weeks as long as the floros are covering the plants ok. but ima tight wad and floros are way cheaper than HIDs to run. but if you do wanna go ahead and use the mh make sure to have it way over the plants to start then lower it until you and your plants are happy. the intensity from a HID can do way more harm than good when plants are small. alot of ppl seem to think floros are not worth a thing, but as long as they cover ok i use them. ive got 12 plants under 8, 4' 40watt floros for 1 month and they are just fine. (check out my avitar for proof, they are at 3 weeks in that pic)
if youve got some extra seeds and squares i would start a new batch.10 days is a long time not not see any improvement, but i wouldnt give up all hope for alil while longer.
good luck n keep us posted