What I don't understand is why you're running a -Spe nature if you don't care about Atk. I mean I kno there's some weird reason -Spe is good on Amoonguss, since going second guarantees the foe will be asleep at least a turn or w/e, but if you want low Spe why the 31 IV? More power Quiet isn't that good a nature-Relaxed is typically bettr despite Amoonguss having lower Def than SpA.
What I'd do is ignore Spe, and shoot for 31/0/31+/31/31/X.
Anyways, I hope that's either helpful or you have some interesting reasoning for your set.
I do have an interesting reason. For the nature, with the EVs I give it, it can 2HKO Primal Kyogre with Grass Knot.
And then, with its EV spread and a Coba Berry, it can survive a LO Dragon Ascent from Mega Rayquaza. For the team I'm running, it works.
The spe IV can actually be whatever. I don't want it to be absolute 0 because I'm running a soft TR team. In the TR mirror (where the effect is not likely to be set up), he gets off an easy Spore on the slow mons.
I'm not going to post the full team. But I've played with it to much success in the ladder, it works.
Now I just need the parents for the cart game.