You could just do echo's or alexa enabled speakers in 8 rooms.... easiest.
Look at accesories4less.com for a basic 7 channel AVR for your 9th room.
Your question #2
..... Just get an Echo input instead of a DOT if you don't want the echo to have a speaker.... or what I did in my livingroom is use bluetooth (or you can do AUX cable) from a Echo Show 5 to a JBL extreme 2. The music plays through the JBL all the time and it makes for a quick portable bluetooth speaker I can grab and go outside without missing a beat.
If you really want to do a better quality WHA than just various Echo speakers then go with the New Sonos amps. 1 for each zone and it is Alexa compatible (or phone tablet as well). Although thats way out of your budget. You are not going to get 26-33 speakers with amplifiers and wiring for $2k not anything near decent anyway. Thats why I suggested various Echo's devices/bluetooth speakers in all rooms.
You could use all Sonos speakers as well and not worry about wiring.
I currently went the route of Echo....
1. Bedroom Echo show and First Alert Onelink Safe and Sound
2. Bedroom Echo Spot
3. Bedroom First Alert Onelink Safe and Sound
4. Livingroom Show 5 hooked up to a JBL Extreme 2 and Polk Magnifi Mini
5. Kitchen Echo Show 2
6. Garage Echo input connected to a Milwaukee radio
7. Basment Echo Dot connected to Polk Magnifi Mini
8. Theater room Fire TV Cube connected to my surround system.
Everything except the First Alerts can be added to a group on the Alexa app
I am thinking about adding a 2.1 system to bedroom #2 with a Sonos amplifier and not using the Spot