Help me design new flower chamber???

Yo guys, like the title says I am starting the planning process of building a new flower chamber. It's going to be a stealth build and I'm using a 6'Hx4'Wx2'D cabinet. So far my plan is to use a 400watt hps with a 6" cool tube for lighting. I'm trying to decide which fan to get because like I said, I want it to be stealth so that means quiet. I'm looking at the s&p td silent series, any input on these? I hear they're quiet. Anyways, should I get a 4" or a 6" for my growing space? My local hydro shop told me to just go with a 4" but I feel getting a 6" and using a speed controller would be a better idea but is it nessicary? I'm not looking to spend a shit ton of cash but I also don't want to buy something twice. Next I am wondering what the best way to hook up the ventilation would be, I want everything to be housed inside the cab. My thoughts are go carbon filter->fan->light->exhaust. Would this be effective way to cool the light and exhaust the cab at the same time? I'm worried about heat issues so any input on how to run shit so my space stays cool would be appreciated. It'll be located in my basement which is undeveloped but because of how it's designed I can't have the cab anywhere near a window to get air from out there so ill have to draw air from inside my basement as well as exhaust into it. My current setup is 4x2.5x1.5 and I have a 150watt hps with a 4" axial fan rated at 95cfm and temps get to 86 on the regular, sometimes more so I'm worried that the 400 watt will roast shit. How effective are cool tubes, my ambient temp of my basement is usually at 68-70. Any other input would be awesome if I've missed anything. Thanks alot. Peace!

I would go with the 6 inch with speed controller if it was me. The way you're wanting to run everything would probably work; although I prefer to exhaust my grow area and run my cooltube with separate fans and separate ducts.

I have a cooltube with a 400w in a 3x3 tent and it makes a huge difference in terms of how close I cab get the lamp to the plants. It brought the tent temp down just marginally, because I turned the exhaust down to match it. I was happy with the temps anyways though. The ambient air my tent pull is also around 70. I get anywhere from 80 on up depending on how I'm running my fans. I usually keep it right at 80 because that's about as low as I can get it with lights on. I exhaust my cooltube out the window and the rest goes back into the room, which is opened to the rest of the house with several fans circulating air in and out.

Hey ganjadog thanks for the reply! Yeah I think I'm with you on the 6" fan and controller, I like the thought of being able to ramp up the cfm if I needed to. Hopefully the controller will quiet things up a bit too. So the way you run it is you have a separate intake/exhaust holes and fan to cool the light and another fan to exhaust your room? If this would keep things cooler I might consider doing that as well...what size fans are you running for your setup?

Yes, that's how I do it. I feel I have more control that way. I run two 440 cfm fans with controllers.