If you're planning on going cooltube + inline fan for the 250 or 400 then I don't see either being much higher than the temps you're already dealing with. My micro cfl grow was running hotter than my 400w cool tube a lot of times. I was able to get it as close to the canopy as you have your 150. You have the space for it, 400w will give you more penetration / bigger buds and is usually within $30-$50 more than 250w. I think it's worth it.
Your plant is gorgeous...the twisted trunk gives her character