Outdoor/pool.deck system

@jin78 

so I thought it would be convenient to be able to stream same music inside and outside at the same time.

If it were me, I'd go with that thought. You might want to think about how much quality, loudness and speakers you'd like the outdoor system to have. In outdoor home patio systems like this, stereo is many times no longer important, and actually doesn't make sense (due to no one sitting in a stereo sweet spot), so consider a mono system. You might also want to consider a (typical PA) 70 volt system. They're really easy to DIY. These 70-volt systems have all sorts of volume controls for outdoor applications. There's plenty of info on the internet to help you along with setting one up. 

Constant Voltage (70-Volt) Audio Systems For Beginners    

I basically have a separate system in my garage. Since the streamer/server in my main system uses Roon and we have a mesh router system, I have a mesh node in the garage connected by Ethernet to a Roon endpoint then a DAC with volume control going directly into monoblocks that power three sets of speakers, one set by the pool area, another in a large covered back porch area, and a third inside the garage. The speakers are hard wired and I have not added a sub.

I was smart (or lazy) enough to hang on to my Rotel speaker selector (see below), which compensates for impedance changes resulting from running multiple speakers and allows me to choose any combination of the three sets of speakers.

This year, I replaced my 20-year old Speakercraft/Weathercraft speakers with Bogen/Near A8T, 8-inch Indoor/Outdoor Speakers and have been very pleased with the improvement.

I have a Yamaha WXA 50 Streaming Integrated Amplifier I use for our pool/deck system with these inexpensive Dual Outdoor 3 ways.

Amazon.com: Dual LU47PB 4" 3-Way Indoor/Outdoor Speakers (Black) : Electronics

Amazon.com: Yamaha WXC-50 MusicCast Wireless Streaming Preamplifier (Dark Silver) : Electronics

Wow, so just as I thought you guys have "enlightened" me to various options. I didn't think about the mono thing, which makes total sense. Also, I didn't think about the speaker "zones" and impedance issues. I guess my best bet is to try and anticipate where I want to end up with this system and build it accordingly.  The more I think about it, I know I'm going to want multiple zones eventually, so might as well plan ahead. Thanks for all the suggestions, you guys def gave me plenty to think about.