Depends how set you are on the Arcam A19 & wireless streaming (in particular, where your router is).
These are the main options I'm aware of;
1. Apple Airport Express using digital optical cable of your choice into a DAC then to your amp.
2. Apple Airport Express into a DAC-equipped amplifier (Marantz PM6005, NAD D3020 / D7050, Cyrus 6DAC / 8DAC, Naim Unitiqute)
3. Your suggestion of Arcam AirDAC into amp
4. An Airplay equipped amp (NAD D7050, Yamaha R-N500 & the just-released Monitor Audio Airstream A100 which includes the feature of direct Airplay, connecting wirelessly without the need for a wifi network)
5. Sonos Connect into wired DAC into amp. This option, unlike those above, use your ithing purely as a controller for your Spotify rather than the streaming source.
6. Spotify Connect equipped products. This is very new and is limited at present to a few AV receivers (from Marantz, Yamaha & Pioneer from memory) but offers streaming again through the AV receiver's LAN connection, using your ithing as a controller only. With Spotify's marketing behind this, there could be a host of products released over the coming year with this feature. However the above-mentioned Yamaha R-N500 is supposed to be getting Spotify Connect as part of an imminent firmware update. Also the trusty Marantz MCR610 has Spotify built-in (albeit not Spotify Connect).
My own experience with Airplaying Spotify is pretty positive. There are very occasional drop-outs (maybe once every couple of weeks) which are usually my router's fault & a quick router re-set solves the issue. Your options may depend on how strong your wifi signal is in your dining room.
My receiver's DAC is supposed to upscale mp3 Airplay streams, and I am pretty impressed with the results. It certainly doesn't set your teeth on edge! I still bother to collect CD's of albums I've played a few times on Spotify for the edge that a digital connection from my CD gives me, but the quality is good enough that my main consideration if I were in your situation would still be the good old fashioned source/amp/speaker balance of sound to your own taste, rather than just going for a product with the biggest list of features.
Having said all that, the Airport Express is possibly the most future-proof should Apple change the Airplay standard somehow in future. The £80 Airport is cheaper to replace than a more expensive product that has it built-in, as I found with my AV receiver; the wired ipad connection only supports older versions than my ipad, so this is no longer an option for me, which is why I continue with Airplay.
Sorry for the waffle, but there are quite a few ways of skinning this particular cat! I hope at least some of it helps!