In addition to the Pi3 and the 7" touchscreen I got these:
DAC:
http://iqaudio.co.uk/hats/8-pi-dac.html
Amp:
http://iqaudio.co.uk/hats/25-pi-amp.html
Amp power supply:
http://iqaudio.co.uk/home/24-19v-power-brick-65w.html
They appear to have updated the hardware since I bought mine, so check for any incompatibilites if you go down this route.
I also got a pair of generic 8" speakers (Pyle brand) that could be mounted in the ceiling.
The amp board only has a small screw type connector for the speaker wires, so you're not going to get anything in there that has a large wire gauge. However, the cable I got was 15AWG and fits fine.
The sound quality is good (I mean we're not approaching £1000+ hifi seperates here, but it's way better than I expected) with no hiss or other cable noise distorting the music. That's all subjective of course and you'll no doubt find differences playing it through your speakers. I'm running Kodi and streaming the media from my NAS. I've got a few external BBC radio stations saved in there too.