Would it be easier to book bands that share 1 or more members?
for example:
Astral Doors->Wuthering Heights->Space Odyssey->Time Requiem->Meduza
or
Valey's Eve->Mystic Prophecy->Firewind
or
Ark->Lande->Masterplan
any chance it will be one of these:
Astral Doors
Human Fortress
Morgana Lefay
Falconer
Running Wild
Demons & Wizards
Jacob's Dream
Grave Digger
Rhapsody
Battlelore
Mercyful Fate