[Mugen no Ken]

The only thing that stops me from recommending Double there would be the "Darker tone" part.

Though it's far and away less campy than Fourze, Double does have its fair share of camp. However, it does have plenty of darker and more serious moments, too. It sort of tows the line between the two, and I've always thought it did it rather well.

At the very least, Double should be added into your queue to watch at SOME point or another, even if it's not your next one.