[TX-NR905 SOUND QUALITY??]

Being open front and back it may be allright just use your judgement.

I have one of this guys fans on top of my Onkyo in an enclosed rack but I probably have 6-8" overhead.

http://www.windywilly.com/

No affiliation but believe he also sells through ebay.

Rich

[TX-NR905 SOUND QUALITY??]

You can always improve be it from receiver to separates or from one amp to the next and so on.

It really comes down to what it's worth to you.

I started having TX-NR901. I thought it was awesome and it was/is for what it does.The most bang for buck in it's price class IMO. Then I got a separate amp and changed my monster cables, then a cheap used pre, then a tubed pre and a new amp etc and on and on.

So bottom line - There is a difference and it can be significant just depends on how far you want to take it. There is nothing wrong with the Onkyo so if you are happy don't sweat it.