Hey guys, shit I haven't made an appearance on here for a bit. I am in the same situation as you upnchronic.
I have been growing in a small stealth cab with hps lighting for several grows now and can tell you exactly what does and doesn't work in my experience.
I have a small 80cm tall, 40cm deep, 80cm wide cabinet that I have pulled off a couple of stealth grows in. I have been using a 150w HPS, no cool tube.
First grow I tried growing 4 lst'd plants under it and i had 3 cpu fans for vent. Plants were ok.. ish but the temps were way too hot and they never reached full potential, they grew fine. Budded, then just ground to a halt due to the high temps.
So the 150w hps and cpu fans failed me.
For the next grow I splashed out and got a proper inline exhaust fan and filter setup and with the same 150w HPS light and it is working a treat. Temps stay exactly where they should be and my plants are a million times better off. After three weeks flowering they were further developed and looked better than after 11 weeks with the cpu fans and high temps. I shit you not... And still no cool tube.
So a 150w no cool tube with a proper inline fan and proper filter works a real treat. (Please trust me, you need it. I open my cab and my house smells).
That is what works for me at the moment anyway. I have pics for you and am happy to help if you need it.
Now, here's the kicker. I'm also thinking of putting a 400w hps in a seperately cooled cooltube into a similar sized cab with my beast extractor fan and filter. So I am exceptionally interested in how this thread plays out.
Consider me subbed. And may the best stealth setup go undetected. +rep for the hps steath setup too man. Good shit.
Check out my old grow thread, might be some help to ya. Shows what can be done with a 150w hps and lst in a small space.