Check out these guys, I love their stuff. Very modular, nicely built.
http://www.salamanderdesigns.com/The thought of "exhaust fans" in a cabinet makes me cringe.
Cringe? How come?
I like natural cooling. It's like having a fan in amp or preamp that isn't well designed to cool passively. It's generally not needed.
That's why I love the salamander stuff. You can have all 4 sides open, or screened, or glass or wood. You pick and choose what's needed on each module.
I have open front and rear and screened sides.
Many components that do have fans will ramp up based on temp. I like seeing things cooled passively and minimize total fan noise.
Stuffing high end components in a closed cabinet then adding forced air to compensate just doestn't make sense to me.