Snap does not make a preamp. The amp with 70 watts per channel can drive outdoor speakers nicely. What source are you using? If you use the global input, you can use Volume Controls per zone to control volume. A preamp or a source that has its own volume control, such as Sonos, can be used as well. There was an issue that may currently be an issue when using a source with volume control, like Sonos, that screws up the input on the amp. I had it happen on one job, in which the sound was completely distorted. They sent out a new amp to replace the bad one. I have not had that issue since though (about 2 years now).