The 990's second zone is purely stereo and works with the analog stereo inputs (so you want to make sure to run stereo analog cables from any source you will be listening to in the second zone even if you use a digital cable for the main zone). If you are wiring two pairs of speakers in parallel and getting a 4 ohm load, all you really need is an amp that can handle a 4 ohm load. If, for example, you use any of Outlaw's seven-channel amps (the 7075, 7125, 7200, or 7700) and plan to use the two extra channels for these bedroom/bathroom speakers, the 4 ohm load will be no sweat for the amp to handle and no speaker selector is required.