I sing with a young persons choir (16 - 35) and we're looking for the dramatic opening piece of music for an upcoming concert!!! Not too difficult and in satb or up to 8 parts...
It obviously depends on what else is going on in your concert, but I like Mendelssohn's 8 part a cappella motet, Frohlocket, ihr Völker auf Erden as a confident and uplifting opening to a concert. It's quite short and easy but does the job that you described. It would be a tad strange if this were the only German piece in a concert, though, so perhaps you could provide some more information?
Harris's Faire is the Heaven is also lovely, but there is no CPDL edition (it was written in 1925), but you can hear it at http://www.youtube.com/watch?v=tFFE92H9sMI to decide if you want to order music. It's antiphonal, gets dramatic in parts, and not too difficult (though there is a part in the middle that has a lot of accidentals).
With more information about what else is on the program, we can provide ideas that fit in better.