The GNC namebrand stuff is not bad. Given this is where you have to go, and given the prices they charge for some other brands this would be a safe bet. I don't know about a cas. protein blend of theirs, but mix it with milk and eat some cottage cheese before bed and you break even.
Get ready for the Glut. hounds to pounce, but I like the stuff. I swear by its ability to keep me from getting sick when I'm really stressed from life/work/workouts.
Hey, you only have $50 there so after Glut. and protein there won't be much left for that super muscle building supp. they sell. How about you just throw some hard work in there--it's free.