Check this out.
My 506 has about 7 inches above it and it runs warm. Especially around the video section and HDMI inputs. Funny thing is the amp sectin is not all that warm.
I know, it's the video circuitry with the video processor that runs hot.
The crazy thing about this, like my Onkyo 805 or 876, used two fans that never turn ON!!!
So Onkyo miss that small, but warm detail here in their design.
Oh well, the customer can always custom his receiver, to suit his needs.

* You can use a small heatsink from an old computer, that fits exactly the size of the video processor chip. Then just apply the appropriate thermal glue on top of the chip, and apply the small heatsink. Voila, custom made.

And if you're quite handy, like I am, you can even install a mini-fan inside of your receiver, right on top of the warmest spot.

Again, voila.
* Another tip for all members and visitors here at Audioholics: remove the top cover of your receiver, and apply some small sticky piece of rubber, all around the top edges of your receiver (3 or 4 in the rear, 3 or 4 on the front, and 3 or 4 on each side, if you do have sides, of course). And voila, no more ringing from the top cover.
** I do that with all my audio/video components.
* Here's another tip: remove the top cover of all your CD, HD DVD, Blu-ray, CD recorder, DVD Universal, DVD, DVD recorder players (anything that contains a disc transport), and stick a piece of thin rubber (2mm), and about 4" by 4" dimension's size, under the top cover, right where the disc transport would be, using carpet tape (double side, extra thin and extra strength adhesive). Then replace the cover. Voila, smooth and quiet as a dead mouse.

** I do that with all my audio/video players.
* Here's another good one: get some squash balls, and cut them in two, right in the middle. Then put each half under the original feet of all your transport players. You need 2 squash balls per player (squash ball cost 0.49 cents each at Wall-Mart or other cheap stores). Voila, no more vibration, or from the player itself, or from another component or whatever is noisy and annoying.
** I do that with all my audio/video players.
* You need some nice spikes for your speakers, speaker's stands, subwoofers, or even under some components. Go to an archery store, and buy some arrow point heads. they come in various sizes and lengths, with screw on type. And they are very cheap too (couple bucks for a dozen), and made very strong, and great looking too. You can easily install them under your speakers by drilling the approriate small hole. You can even tage the feet of some of your components, and screw these arrow points in place. Or if they don't fit the original holes of the feet, just drill some new very small ones under the component you wish to arrowed (or woed). Voila, you got yourself some serious piece of hardware for just few pennies. It looks great, it does the trick very nicely, and it sounds good too, no kidding.
===> I got several (many more) other good tips like these, I will eventually enumerate them during the course of my stay, here at Audioholics; so everyone can benefit from them, like I do myself.
==> Next time, I'll give you some nice tips on how to isolate your component's racks or shelves or entertainmemt centers. I can even show you how to build very easily the best shelves for your audio/video components, with the minimum time and tools. Even a young kid can do it. And if you like acrylic, like I do, I'll show you how to work with it with minimum fuss, for the best looking shelves around. Very easy to do, and gorgeous looks. Women just love it.
=> And I'll show you more tips on how to further cut room vibrations and best isolation for all your audio and video components, with the simplicity of a deck of cards.

You won't hear a think in your home theater room or living room anymore, guarantee.
But you'll hear a fly flapping her wings then, or a mosquito planting his dart in your skin.
Cheers,
Bob
>>> Important note: I don't know how to do that myself, but if someone can transfer this post by quoting it in my own thread called: * Everything Important To Know About A/V Surround Receivers, But Were Afraid To AsK. *, I would greatly appreciate that, so I can continue in a single thread, where most of my life is going now.
And this is for the greatest benefit of all.