Just watched that a few days ago, and goddamn this is some hotblooded mecha action. Episode 3 was understandably dull, and 6 was disappointing, not bad but disappointing. Seriously though, first time i've gotten hyped from the MC screaming. 9/10.
As to your description of Steel Ball Run, i have to disagree with you. Strictly speaking, you don't "need" to read the other parts to understand it, but the viewer would be missing out on a lot of throwbacks to Parts 1/2/3 (I say part 2 but i can't remember any).