Spotify Connect is the “killer app” for me as I have a couple of amplifiers with the inbuilt connect client. That being said I use plex-amp to listen to all of my ripped CDs (being collecting since buying Brothers in Arms as my first CD when it was originally released), which is Spotify like for music on the go, and it’s loss-less (then I use Bluetooth headphones :-( )
Short answer is yes. You can mimic, having only one SSID for your wireless network by setting your older access points to the same details as the dream router. But I would recommend having a different SSID for your older Access Points, and replace them with Ubiquiti APs eventually (U6-lite etc) which then will be adopted in to UniFi, and you can run Multiple SSID (and maybe even VLANs if you add managed switches)