Mind is totally correct about the outtake and the lighting.
A 150 is going to be much more effective, because it won't cause half as many heat issues in a grow room that size. The purpose of having a HPS is to get those dense buds, but if you have too much heat it (Like you'd get with the 250) will prove pointless. The heat will make your buds all fluffy and stringy like.
I have a 2' D x 4' W x 4' H grow cabinet room I made myself, this is basically the smallest you can really get with a 250w. Trust me I've tried a bunch of different grow room designs lol, and this one seems to work best, for me anyway.
You can try and lower the noise fans make by buying a bunch of computer fans and putting a noise suppressor behind it. You can find those at any computer store or online computer store. They are basically foam inserts that you put behind the fan before you screw it in, the foam reduces vibration and some noise.
I don't think you're going to be able to do a stealth 250 grow honestly, the heat will be too rough to manage, especially with the ballast above the grow cab. Also because it is stealth you won't be able to get the proper ventilation that you need. I'd stick with a 150w, unless you can make it a little bigger and get good ventilation.
Hope this helps
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