Centralized multiple zones from a PC

My current setup is as follows:

ThinkPad to 3x Startech 7.1 USB cards that feed 12 zones (mostly stereo, a few mono).

Running MS4L, which is an LMS/SS-Lite based setup. It lets you do the following:

1. Separate out USB sound cards into whatever mix of channels you want. You can take each 7.1 card and have 8 mono channels, 4 stereo channels, or a mix of both (e.g., 6 stereo and 2 mono).
2. You can have zones that overlap in inputs, so you could have a 1st floor zone and a living room zone.
3. LMS plugin support for Airplay, Spotify, etc.

But....

It is a pain to setup. When you have multiple USB interfaces, they are assigned to channels in order of boot and can end up mixed if you accidentally pull a cable. You have to walk through and figure out which channel is which manually which is tedious as hell. Etc.

So before I bang my head against the wall setting it up again, I want to see if there is something better.

Key requirements:

1. Let me split soundcards in the same way into multiple zones
2. Spotify support is absolutely required
3. Interrupts for doorbell and other alerts (mp3 or other)

Nice to haves:

1. On the fly synced grouping
2. An easier install
3. Room correction for each zone
4. Headless operation
5. Airplay and UPnP support

I looked, and most of them are RaspPi based (e.g., Moode, Volumio, Max2Play). I could do this, but 12+ Raspberry Pis isn't that cheap either and it feels a bit silly to have a bunch racked up instead of one more powerful system.