help with lighting

hey guys want some peoples opinions on what i should do with my lighting...i currently run a 250w mh in my veg tent and a 400w hps in my flower tent thats 165l x 160h x 65d... i was thinking about buying a 600w hps and run that in my adjustawing reflector...i run scrog and was wondering would this light be ok heat wise in my size tent.. i run a 5inch extractor constantly and temps are around 70f while running my 400 ...

to save money on electric costs i was going to run my 400 the first couple of weeks then switch to the 600 but not sure when the best time is to switch,

so to summarise whens the best time to switch to the 600w light?
will a 600w hps in adjustawing reflector with extractor constantly running be ok heat wise in my size tent?

thanks in advance for any help

Simply put, there is ABSOLUTELY NO WAY that you can effectively run a 400w hps in that size tent once the days get warmer. You might get away with it in winter.. but not on a summers day. Sure, your plants may survive, but they won't thrive. The temps will be over range all the time and the plant won't be absorbing CO2 which it needs for photosynthesis.

You'll get far better results in the end if you choose to use the 250 watter. I have virtually every bulb going.. but I now only use a 250w DS bulb, and maybe a 400w MH on a cooler day. And if it's cold, I may add a 250w CFL too for side lighting. I'm getting twice the yield over when I was using a full kilowatt!!

iv run a 400w in the same tent for a few yearsnow with no problems...i yeild anywhere between 10-14 ounces each grow even in the summer..the temps only reach 80f at the very top of the tent.. while canopy is always around 70f.. i have friends that run a400w hps in a similar size tent that get heat issues but they havnt got extraction dialled in and they only run 4 inch extractors...i also have a 6inch extractor just incase it doesget very warm...how much temperature rise would i expect if i switch to 600w hps?

try growing on your basement floor and using the air intake very low to the ground. Also its good to have your exhaust hooked up to the light so it sucks the heat away. Maybe you could have the exhaust go outside so it doesnt build heat up in your area. Why switch to 600w hps ? try adding some t5's in the 2700k-3500k and hang em. they have 2 foot ones that are pretty nice at home depot around 23$. i think they have the double ones for 30$ also. a 400w with a 4ft light mover and two double bulb 4 foot t5's works great IMO. the mover is 100$ and the t5's were 35$ each so 70$