IBP or swift seem to be the best, and quite consistant as far as size and quality. I would approach your butcher and see if he would consider supplying you with a contracted amount each week/month for a certain discount. He would make out with a better discount from his supplier, and as long as he didn't get stuck with 20-30 cases some week that you decided to go elsewhere, it should work well.
remember, the finished product can only be as good as it started out. If ya buy discount meat or inferior stuff from discount stores, the end product will suffer.
Like they always say, "you can put lipstick on a pig, but its still a pig".
I think ya know what I mean. If you wanna open a rib shack, you want to have something that folks will drive the extra distance for and pay decent money for! I wish you luck with your endever!