I don't have a good answer to your question, but I have some choral musical recommendations I've found powerful in the same way that you find Slava! powerful.

I'd recommend the Bach choral works to interested readers. The major ones (St. John Passion, St. Matthew Passion, Mass in B Minor, Christmas Oratorio, Easter Oratorio) are all worth listening to, but there are also a couple hundred of cantatas. Unfortunately, the sheer number of cantatas makes the collection overwhelming and in my opinion there's an issue of uneven quality, but there are some really excellent pieces among them and I've found it worthwhile to spend time with them as well.

I also really like the Brahms German Requiem, particularly the sixth movement.

Will add more examples as they occur to me.