Much of this depends on you being clear about what your goals and expectations are and then adjusting your budget accordingly. While you may be happy to do grunt work, there is a lot about a professional A/V installation that may ask for more training than the typical person may have. Pulling enough cabling, labeling things properly, avoiding certain locations that could cause problems. It's nice to offer, but in most cases where I've had the customer 'help', I've had to go behind them and correct mistakes made, or troubleshoot wiring issues, or pull additional cables which the customer didn't put in place. Every customer that does it, thinks they could do it properly, and that was part of the problem.
For long term growth, pulling all wiring back to a central location with plenty of room for growth is important. Pulling the proper wiring to the different zones is important.
Sonos is great, but it's not 'cheap', and while it's a great solution today, it didn't exist ten years ago, and may not exist ten years from now, which is something that should be kept in mind if that is the complete solution to your requirements.
The Play 5, for example, while it can get louder than some speakers, isn't going to be anything like a 'club' level speaker. If your 'party' goal is to sound like a nightclub, then you need to make the astoundingly clear. You also need to identify that requirement from yourself to ensure that nobody is confused about what is expected.
If you have a Marantz receiver, I would likley use a Marantz amplifier to go with it. They are nice, and they do work well. But, good amps really are good amps. The Niles ones are far more designed for lower power and are not what I would use in a system that needs to 'crank' at any point. I might opt for some Crown Class-D amps and some much, much better speakers in rooms that need to get really loud. There is a definite difference between speakers which have high quality acoustics and speakers which can sound like a nightclub. I've literally had people who have had to yell to be heard over the speakers, complain that it wasn't loud enough.
So, all of this matters and is going to be driven by you. I would certainly take a close look at the subwoofers mentioned above. HSU/SVS, etc.