I'm not sure if this has already been discussed (i did a forum search and couldn't find anything).
Anyway, I was just watching The Sopranos before (a fine show i might add) and i stumbled across the second GTA 4 trailer again. At 0:34 - 0:37 when "Fine, you want my word? You got my word" is spoken, it sounds extremely similar to James Gandolfini's voice (Tony Soprano). Does anyone else think so too? Could he be the voice of a head of a mob boss family as he is in The Sopranos? Seems fitting indeed.