even with the cooltube setup you think it would still get too hot?
OK... technically ANYTHING can be done. yes if you have a fatty fan blowing through a cooltube you could keep that cabinet cool enough, but the radiant heat from the light itself is going to prevent you from letting your plants get real close to the bulb without light burn. Having a fatty fan blowing through the cooltube isn't overly stealth if it is in your main living area.
Somebody above posted that "if you use floros you don't have any heat problems" and that is incorrect. Floros generate plenty of heat... not as much as hps, but certainly something you have to deal with. In my 19x14x30 flower cab I run about 250w of CFL's and if I turn off my fan I could cook a pizza in there! I just measured my exhaust the other day and whenever my lights are burning, my exhaust comes out of the cab at 120 Deg F... I'm not sure if my thermo goes over 120F, so it may be even hotter than that. The temp inside my cabinet is about 75F. Don't kid yourself thinking that floro cabinets are easy to cool. Easier than HPS, but still involves some time to dial it in.
the biggest difference between hps and floros is penetration. The key to sucessfuly growing with flouros is designing so that you don't need the penetration. More, although smaller, budsites and a fairly even canopy...
The 4 most effective ways of using flouros are side-lighting, SOG, ScrOG, and LST. With side-lighting you simply light from multiple angles so the whole plant gets light. With SOG (Sea Of Green) you do many smaller plants, usually strait from clone to 12/12. ScrOG (Screen Of Green) is done by putting a mesh screen such as chicken wire over your plant(s), and continually training the plant to stay under the screen until it is about 3/4 filled, and then once you switch to 12/12 you let the budsites pop through the screen and trim off all the stuff below the screen. LST (Low Stress Training) is similar to ScrOG except that instead of using a screen, you train the plant(s) by tying branches to the edge of the pot to keep it low and bushy.
All work, and all have their pros and cons. Probably the best for maintaining an even canopy is ScrOG, but it is also the most labor intensive and it takes some time to go from seed/clone to a filled up screen. Most productive would be a perpetual SOG where you run 8 or 9 groups of clones and every week you harvest 1 group and then put a new group in. This is usually done with smaller pots like a 4x4 square or soda bottles that are made into pots. SOG can be quite labor intensive with all the cloning and since the pots are smaller they require watering almost every day. Some people shy away from SOG because the plant count is much higher and could mean legal trouble. Side lighting is pretty simple and with the advent of thin, tubular florescent such as t-5's or PL-L's you can put a lot of light into a small space to maximize penetration deep into the plant. LST is my current poison of choice and that works well for me. I do a semi-perpetual flower cabinet that is fed from a tiny little veg cabinet. There really isn't much labor involved, I can use a large enough pot size so that I don't water every day, and since there is no screen in the cabinet I can veg in one cabinet, and run my flower cabinet perpetually with 3 or 4 plants at any given time.
As for building a cab... if you aren't handy and don't have tools it may not be a great idea. Ventilation, carbon filtration, and light sealing are all rather sizable challenges. You can plan and plot all you want about these things but when it comes down to it trial and error are required. Most every cabinet needs tweaking before all is said and done. Buying a premade peice of furniture or a cabinet makes things easier than starting from scratch. Then you just modify the interior. Building your own is cheaper in the long run but there is the labor aspect you have to consider.
Hope some of that is helpful!
Jed