The only time I can think of when Piracy negatively impacted software sales for a console on a large enough scale to really matter was the Dreamcast; with no modification necessary, rapid expansion of filesharing, and inexpensive (readily available) game media a large portion of the Dreamcast's small userbase stole games.
The second someone has to open up their system and modify it the rate of piracy drops dramatically; most people are not comfortable with modifying something that cost them $200 when they stand a decent chance of destroying it.
I would say that the small portion of a userbase that does tend to steal games can benefit the system because these gamers are often far more vocal and will promote the system to less knowledgeable gamers.
