First of all, Mitch's cable does control the audio part of the tuner. You have two RCA outputs on the Tuner for your audio. If your LINE IN does not work correctly with the Card, I think it should, you can allways try the CD IN on the motherboard and see if it makes a difference.
Software wise, if you downloaded the newest version of RR then you can see a subfolder in the RR Directory, called HD Radio. There are six files in it. Double Click the file called
"runme1st". After that run RR Conifg.exe and under the RADIO settings select HD RADIO and the Audio Line you use for the Radio.
Next, look in the RR.ini file under the RADIO part, there you find this.
radiomode=8 >tell RR to use HD RADIO
allowallfreqs=false > Tuning of the Frequecy steps (88.5,88.6,88.7 and on)
radioline=1 >wher the audio comes from
userbds=false > for PTY info false for europe, true for USA
hdradioport=1 >the com port you pluged mitch's cable in
Now, when you click on RADIO in your skin, you should hear a click in the tuner and it should start playing.
Look in your mixer and make sure you don't have anything muted that you need.