I forgot about the DSR505. I couldn't remember if the 500 series had a 505 model. I know there was a DSR605 receiver which has since been retired. That one featured more options for outputs and had a front display. That would have been a suitable replacement for the DSR505. If I remember correctly the DSR600 is simply coaxial out and HDMI out only.
$99 seems steep considering this receiver is 6-7 years old now. I figured they would offer it for $30-$50 per unit to upgrade.