I put my seedlings under a 500w HPS and it works perfectly.
I think they'd grow beautifully under the 600, as long as you make sure the temp is fine and they aren't too close to the lights.

When the taproot comes out, I personally keep them out of the light until I see a sproutling. At the first site of the dirt being lifted, I put them under the light so photosynthesis can start asap.

Lowryders sound like fun.

<3