yeah if you want to keep them short i'd get the 6500k's (creates lush foliage, helps the plant bush out) and get as much light as close to them as possible.... plants generally grow taller in lower light situations in order to break through the underbrush (evolutionary adaptation) to get access to direct sunlight...

so the plant basically perceives weak light as shaded sunlight and says "hey man, i need to like, get up there above that fuckin bushtree next to me so i can get that good good light shine on my leaves so you can blow trees"

that's why well set up grow ops plants are usually very short but wide and bushy in the veg stage. as an example i had to temporarily change my set up, and i went from roughly 150 watts of cfl's to 50 watts for about 3 days. i saw 3 inches growth in those 3 days, but it was ALL STEM.