I'm new to L3 switches as well, knowing the concept for some time though.These two Amp devices start audio synced and get async by time. Is there any setting to avoid something like this? Or should I focus on the devices?
However, and I could be completely wrong here, the only "tuning" you can do with a switch is with larger packets called Jumbo Frames (and both devices must support it). IIRC, that only helps for very large file transfers - I don't see how that can help streaming though.
There's also some QoS tuning that can happen across VLANs. But if you haven't configured QoS (and you know you have because it required precise settings of what to prioritize in packets), then that's not an issue.
Network really wouldn't have much of an affect when it comes to eventually getting out of sync'd. This sounds more like application timing running on the devices.
IMO, start a new thread about this as I don't think it's network related.