no, they would not likely fire the 600s. they may, but it may overpower the starter in the ballast. im not an electronics whiz though.... but im looking at the option of using multi 400w, 3 to be exact, on a 1000w ballast. a 1000w will fire and run 2 600w lights fine with the appropriate splitter, but will overpower 2 400w. but 3 400w would be equal to 2 600w, but im unsure of the powerup ability of the starter.
imo, if it works, you ll stress the bulb some, thus shorten its life. If your on 400W HPS or and want more light, imo, your far better off just moving to the 400w Philip CHM Retro White bulbs. better penetration, more light spectrum, uvb, and can be run in an open fixture. they also run cooler than the 400w HPS or MH bulbs. the Philips CMH runs about 55 to 60.00, runs on an HPS ballast, and is rated for a 2 yr life span with minimal lumen loss over that period (that rating is 2 yrs running 24/7).
they are directional as well, so you ll need to get a Vertical or Horizontal version depending on your application.
