I have a couple of 4ft T8's with 6500k bulbs now, needed to double that, and am going with a high output 3 bulb 4ft T-5. The 15000 lumen is 40% more than two, 2 bulb T-8's.
$73.00 includes bulbs and shipping.
http://www.ebay.com/itm/T5-Grow-Ligh...YAAOSwVFlUFrjS