The amp dertermines whether you need to upgrade electricals not the sub. Using the same amp with each setup, you will be fine on that front.
The Kodas are new to the point that I doubt that many people would be able to give you an hinest opinion on them. Why are you choosing between 1 12" Brahma and a 10" Koda BTW? You should be able to power 2 10's with that amp, no problem. Or you could just wait until the 12's come out this summer and get one of those. I'm guessing that the Kodas are more efficient and will do better with 500W than a Brahma at the cost of a larger enclosure.