Three cories are fine together, I've never heard one complain.
May I recommend Jewlie Cory Cats, they are sometimes hard to find but they are the best looking ones. The rams should be fine, but you should integrate them v. carefully and slowly into your tank. I usually take one hour to integrate new inhabitants if they are going to have their pH changed. Ask the store what pH they are keeping the rams in, and do a pH test right before you go to pick them up at the store. If it's more than 0.5 difference, than you need to be sure to add small cups of your tank water into the fish store bag they are in over a period of one hour. I've had a 100% success rate with this method.
May I recommend Jewlie Cory Cats, they are sometimes hard to find but they are the best looking ones. The rams should be fine, but you should integrate them v. carefully and slowly into your tank. I usually take one hour to integrate new inhabitants if they are going to have their pH changed. Ask the store what pH they are keeping the rams in, and do a pH test right before you go to pick them up at the store. If it's more than 0.5 difference, than you need to be sure to add small cups of your tank water into the fish store bag they are in over a period of one hour. I've had a 100% success rate with this method.