If your gonna have an actual concert that will make a real impact it will need to have at least one main stream artisit for it to get any kind of attention. This fact is sad but true. If we can get that then the 3 best days for such an event would be the night before the straw poll, the night of the straw poll or the night before the vote. If this could actually get done properly then it no doubtedly would be a huge asset, but the chances of pulling this off are very slim.