I've set up a delay line in a church where it's sixty feet from front to back. The delay is hardly noticeable. Most people kinda think there's a room echo. I set the speakers that fill in sound from the ceiling with a 30 msec delay and it's almost impossible to hear any delay now.

Yes, it's possible to hear 30 msec, but it's not at all easy. You probably won't notice if there is that much delay.

I expect buzz will have a good opinion on this.

By the way, I have an Atlantic Technology WA-5030 sitting on my desk (in the box). It's got a wireless transmitter and receiver. The receiver has a 30 watt (per channel, I think) output. This would do exactly what you need. There's no digital delay, only analog delay, which is in picoseconds.