Since it is just a 500w motor I felt safer limiting it 1.25 to be about 1200w (mine is a 30a kt sinewave where the upgrade is 35a) as to noise, mine sounds about the same as stock, I really don't know aything about the 25a upgrade kit other than it is marketed as a Rad power bikes upgrade so it should work. I just got a kt sinewave controller from the kunteng ebike factory store on Aliexpress and a adapter cables for the battery from big game bikes, Electro bike world also has them and adapted that instead of using the upgrade kit, only saved about $50 going that way and does require more work. On my DIY bafang 750w rear hub fatbike I run a identical controller not limited.