reefrocks.net has some great dry rock and the price is definitely right. The guy will most likely even call you to ask what kind of scape you want to make before he ships it, but if you have specifics you can call him and he will accommodate you.
His sand is great too... real carribean argonite collected in the Bahamas, and it is FREE. He sells it for the cost of shipping (~$15 for a 40lb large priority mail box).
He ships via FEDEX home delivery, which took 4 days to Chicago. I would imagine you would have it in a couple of days.
Sorry, I know it looks like an Ad for the guy, but he does great work. My only complaint would be that he takes a few days before he ships, but it is worth the wait. I think with your 30 lbs you already have, 50lbs will be more than enough.
This is 50lbs of his rock in my 57 gal