If I am understanding correctly you have a little over 100 watts of light in there. I would think 250 would be the bare ass minimum you would want to use for that space. I run a space about 1/2 that size and my flower light is 600watt. I veg my clones to about 6" in height on over 250 watts of T5's which is likely what that long light will turn out to be. Also, soft white is good for one thing and one thing only, reading books. Try using a 6000k spectrum for vegging the plants and then when you switch to 12/12 use 3000k bulbs and lots of them if your not going to be buying a large over head HPS light. Forget the equivalent numbers: 26watts = 100 watts. BS. Look at the amount of power going into the bulb, count those watts and don't stop till your well over 250. Everything else looks good. Just watch the heat with all the new lights you will need to be adding to get bigger plants.