With the closing of the summer I've been more focused on outdoor activities lately, but to answer your question I have the chromecast plugged into an older Dennon amp (789?). The other rooms are powered by Pyle 160 watt amps
that are connected to the NFC bluetooth receivers. The amps are audio-only, so the chromecast won't work easily with them. I'm considering replacing them with some cheap HDMI-equipped AVRs.
I like the NFC for its convenience - any of us (or our friends) can tap the wall and play our audio. Even my daughter's iPhone devices can manually connect. So it's perfect for audio-only rooms.
The Chromecast is great for the main media room. I think its audio quality is better than bluetooth since it's a direct digital connection, so that's a plus. In the other rooms audio quality isn't as discernable since the ceiling speakers aren't exactly audiophile-quality. The chromecast is really fun when a group of people are connected to it and we're taking turns sharing funny/entertaining youtube clips on the big TV.
I'd highly recommend using the chromecast for your music option if you already have your music on Google Music (since that's the only music it can stream). For $35 or less, it's a cheap and easy way to connect your audio system to your music library. Plus it has the added benefit of having a really great, convenient interface since it uses your android phone / tablet (and iOS devices as well). I don't really use it for Netflix - we have hardwired Rokus for that (plus they do Amazon and Hulu).
Even if you don't use google music I think it's worth taking a look at it. We have a google account just for music, so all of our devices (including our kids') have access to the entire library from anywhere (inside or outside the home).
Also there have been some great deals on 1st gen nexus 7's out there ($130 or less).