Volt Tackle Pichu / IVs problems

[LimeSoda]

Hello, I was wondering if I should keep my current Pichu that knows Volt Tackle or not. It's nature is Quiet so it's Sp Att is raised but its Speed is lowered. I suppose it is not the best nature since Pikachu utilizes Sp Att and Speed, but the thing that makes me want to keep it is that its IVs for Sp Att are perfect (31). If I were to max out EVs in Sp Att, its Sp Att would be the max possible, correct?

I dunno, I think I'm just going to keep this one since the chances of me getting a Modest Natured Pichu with 31 IVs in Sp Att would be 1/62, since the everstone trick to breed for Modest nature only works 50% of the time. Do you think its max Sp Att will make up for its hindered speed?

[Agonist]

You can replace the parents as you go along. For example, if you used that Pichu you just hatch as a parent, it would increase the chances of passing down a perfect SpA IV. That being said, Timid would be the ideal nature, but Modest works too.