The 990 has three buttons for surround modes. "Dolby" will scroll through any available Dolby modes, "Stereo" will scroll through any available stereo modes, and "DTS" will scroll through any available DTS modes. Which modes might be available with each button depend on what the incoming signal format is. For a PCM stereo or analog stereo source, for example, "Dolby" would offer some Pro Logic II modes as well as Dolby Virtual Surround, "Stereo" would offer 5-Ch Stereo (and 7-Ch if you have surround back speakers), Stereo, Bypass, and Upsample, and "DTS" would offer NEO:6. For a Dolby Digital 5.1 source, on the other hand, "Dolby" would offer DD along with DD EX and Pro Logic II modes as well as DVS, "Stereo" would offer Upsample only (which uses straight Dolby Digital decoding along with upsampling), and "DTS" would do absolutely nothing. Page 13 of the manual has a good overview of the modes offered by the 990.
I'm really not sure about using your cable TV as an antenna for the radio. The cable would serve as an antenna, true enough, but I wonder about the actual cable signal overriding that natural antenna effect. They're covering pretty different portions of the spectrum, but I don't know if the tuner would disregard the cable broadcast or get messed up by it. Unless somebody around here has done it successfully, I'd call or
e-mail Outlaw before doing it to make sure it won't have an adverse effect on your tuner.