Controlling heat is a big problem with HID lights used in cabinets. If you are using an HID light, pay up and get an inline or squirrel cage fan. You can find a 6" Vortex fan for $150 - and it draws 450CFM. A 265 CFM squirrel cage fan can be found for slightly less.

But don't just look at CFM when shopping for fans. A 450 CFM inline fan is tremendously more powerful than a 450 CFM "duct booster" fan or muffin fan (The fan pictured above is a muffin fan). The physical mounting of the fan is also something to consider.

I believe I have 8 different fans in my arsenal right now. Inline, squirrel cage, duct booster, and a couple of muffin fans.... Keep your options open....you'll thank me when you turn on the HID light and the temp reaches 100F in your box.