vermont karaoke and billiards is our go to spot.. private rooms and everything... they serve food, but i can't remember if they serve sushi.... it's a great vibe though... and actually, i think you can bring food with you (if you sneak it in).. although we've brought cakes on various ocassions and nobody seems to bother you once you are in the room. they also have a full bar and pool tables if karaoke is not ur thing.
new japan in santa monica is okay on a college budget, but they used to have karaoke nights.. .you might want to call to see if they still do.... i haven't been there in YEARS, but i did a quick search and it doesn't mention karaoke... although it does mention that the beef teri is the dish to get.. unfortunately i didn't see sushi reviews. the place is in a crowded area though and you are lucky to get a parking spot...
i think stick to k-town and bring your sushi with you. =)
happy eating and singing!