After watching this video as well as others (and of other corps) but more or less this one, I, being pro amp have realized something that those who are against amps and especially placing a mic in front of horn players that this is solely for effect. It's more evident with headphones on but I know no one really needs to be mic'ed in DCI. To me the sound they are going for it that reverb concert hall sound as evident by the backed up electronic sounds. I think it's quite tasteful. Great work!
