I'm pretty happy with their names after all.
As Lily mentioned, 'Heart of Gold' plays in a little, I mean that's almost a part of the plot in the game, that the player has a heart of gold (kindhearted, call't what you want), and thus kinda turns the badass rival to the 'friendly' side. At least that's what I thought when I played it at first. They wanted a similar thing for Silver, and I think Soul worked pretty well there too. They basicly mean the same thing, so...
I guess I'd have sticked with whatever name they decided, although playing DirtGold and CrapSilver doesn't seem just as fun.