What are you using to vent the "average" family room type cabinet?
I've used a remote fan type from Holovision and duct type from Cool Components. Neither worked really well from my view, cabinet was still pretty warm.
What are you using that'll work in a small area to vent to outside or the next room? Within most den/ family room cabinets there usually isn't much room.

How much air was really being exhausted with the fans you tried?  What is the cfm rating?  Can you just use an exhaust fan that moves more air?  Also, did the units you used have a sensor to regulate the speed of the fan?  Are you just exhausting air out or are you pulling enough air in?
what models have you tried?

My first method of solving venting problems was to carry a 12VDC fan and power supply I bought at a surplus store, and plug that into the switched power output of the AVR (which aren't always available any more). I found that was a bad idea because I couldn't always get the same, or even same size, fan; also, if they made any noise at all the system revved up like an old WWII airplane when started up. And the fan ran all the time the system was on, usually not a necessity.

I then carried one particular model I got from Grainger, solving only the repeatability problem. But all is now solved by carrying the ATM System 3E. Benefits:
~Always ready when needed
~Always can have the same item in stock
~80 mm fans use 3" hole, not hard to cut
~Thermostat means system startup is ALWAYS silent, and fans don't run all the time
~Two resistors allow choice of fan speeds
~Two fans allow push in/pull out or dual push in* venting if the air can easily exhaust
~Use only one fan and you've got an extra for the bin


*my dad, an engineer, made the point that turbulent air flow cools better than laminar air flow. The upshot is that blowing air onto something removes more heat because the air motion is likely to be less orderly than air sucked over and past surfaces.

I use Middle Atlantic's CabCool at the top of the cabinet, then drill some holes on the bottom lip for air intake. It works great and is very quiet.

+1

Cool components also make good fans.

BoraGear if you like it to be quiet too.

I love this cool components fan:

[Link: coolcomponents.com]

They are big enough so that you move a lot of air but you adjust the voltage on the ac adapter to manage speedso it isn't too loud. I can't stand a loud fan. You can add a cool components thermostat too if you want manage it that way.

andrew, that's a neat unit.

I find that no matter what you choose, you're WAY ahead if it has a thermostat of some sort. When you turn on the unit and it's cool, you don't want to hear the fans revving up. When you turn off the unit and it's hot, you're probably leaving the room, so it doesn't matter if the fans make a bit of noise. In between, Nicholas Cage is crashing shit, so who can hear the fans?

Right- laminar air flow is for moving air from one place to another in a duct, not actually for the heating or cooling. Convection causes turbulence although devices or heat sinks that are placed in a contained space using laminar air flow will cool well but the flow rate needs to be sufficient. That, by itself, causes problems in this application because the air speed/fan rotation makes noise.

I did a project a few years ago and the cabinet for AV equipment was not very large. I was amazed when the cabinetmaker asked if I wanted slots in the shelves. Since I knew the cabinet would be closed most of the time, I made sure of how much of a gap was at the doors and installed a small flexible aluminum duct with a grill at the top of the rear wall, going down to the basement mechanical room. This terminated in a 4x4x6 gray electrical box, where I mounted the fan. Since the receiver had two convenience outlets and 12V triggers, I was able to use the outlet for a wall wart to run the fan whenever the system is on. The cabinet only has a receiver, BD player and Scientific Atlanta cable box, but I wanted to make sure it was always cool enough and it has never been a problem. The distributed audio amp is in the same mechanical room, so its fan isn't a bother.

Speaking of fans, the job I'm working on has one of these-



143" diameter and yes, those are winglets on the blades.

I use the Cool Component t alt and hiflo combo every time. You need to make sure their is enough air in take to turn over fresh air often enough. Quiet and the thermal couple works great.

Nice thing about the CabCool is that one quick hole saw cut and it slips into place. Snap the grill on and plug in the fan. I have used ATM fans for more cooling, but they are not as quick to install.

I think this is the very kit (with T-Stat) that I got from Snap some time ago. Still haven't installed it in my house as winter kept the room cool. 
Thanks for the reminder that I need to get this installed soon as temperatures outside warm up.

ah, is that a big ass fan? we have seen several of those throughout the years, they are really cool!

We have one of those in the local Latitudes gas station. That thing is fricken huge.
[Link: plus.google.com]

Active Thermal Management system 2, system 2+2, or system 3 kit for 90% of our surround sound systems. Many of these include a DA amplifier.

They have several white papers on cooling cabinets. We also use there inline fans for larger systems in closets.

We have tried all the other brands and always come back to ATM!