You need to come up with a budget and wish list before you go any further. Also list out your priorities:
- Do you want music in the background that just has to sound "good enough", or are you an audiophile?
- Do you only want to play music from your phone? What about other sources?
- Do you want to tie the speakers on each floor with TVs? Do you want to be able to sync TV audio and video throughout the house?
- Do you want surround sound setups in any rooms, or is stereo or mono sound OK?
- Do you want equipment hidden or out in the open on shelves/countertops?
As mentioned above, wireless solutions such as SONOS and HEOS are good if you don't want to run cables in walls, and if your primary concern is background music from your phone. They are not the best though for engulfing sound, or for syncing up multiple speakers with TV sound due to wireless delay.
If you want to go all out with in-ceiling and in-wall speakers, wired to a central location, with audio and video distribution throughout the house, then get ready to open your checkbook. Especially if you hire out the work.