under $500 used which a/v receiver or processor

I second the Onkyo 605 for $399 at Amazon. In addition to HDMI connections it decodes the advanced audio formats (Dolby True HD and DTS-HD Master Audio). If you have, or plan on having a HD display, blu-ray, etc. in the future, you'll regret not having these features.

Rrekstad, as indicated by Saki70, the 605 does in fact decode Dolby True HD and DTS HD Master Audio.

http://www.onkyousa.com/model.cfm?class=Receiver&m=TX-SR605&p=i