The new Apple TV is a great device, for using with a TV. But if you want to connect it to an amplifier, to stream music over AirPlay, then it’s not for you. Here’s what the back of the device looks like:
You’ll notice that there is no longer a Toslink (optical audio) output on the back of the Apple TV. The only option you have is HDMI; this is fine to connect to a TV or AV amplifier, but if you want to connect an Apple TV to a DAC, and then to an amp, you’re out of luck. Of course, one option is to use both: an Apple TV 3 for music only, and the new Apple TV for videos, games, apps, etc.
You can still buy the Apple TV 3, which does have a Toslink output; Apple hasn’t discontinued that model, and I speculate they’ll keep it around for a while.
And if you want to stream music to a speaker that doesn’t have AirPlay built in, then you’ll need an AirPort Express, which has a standard headphone jack at the back. (The AirPort Express has a combined analog/digital jack.)
It’s also worth noting that the new Apple TV also only has 10/100BASE?T Ethernet, and that Ethernet is slower than the 802.11ac wi-fi.
Update: As a commenter points out, HDMI allows for DRM, whereas Toslink doesn’t. This could be the reason for the elimination of the digital optical output: since you can stream Apple Music on the Apple TV, perhaps Apple needs to ensure that you can’t easily copy music you play from it.