Complex sentence: The single received extensive airplay in Michigan and propelled the group to regional fame in the area, which resulted in more gigs and, at the Den, the band opened for prominent musical acts including The Amboy Dukes and The Gentrys.
Split into simpler sentences: The single received extensive airplay in Michigan and propelled the group's fame in the area. At the Den, the band opened for more prominent musical acts including The Amboy Dukes and The Gentrys.