...I find that anything from 4100k to 6500k will work.
For flowering, 2700k is preferred, but if you can find some 'round 2000-2100k, that would be killa... to better simulate 'fall' lighting.
W4llM4rt is your friend here. You can pick up a box of 6x26w CFLs for like 20bux in my 'hood, in either 6500k, 4100k, or 2700k. You can also pick up 'shop' lights in 45w/4100k/3000 lumens... for 15bux ea!
Pack 'em in...