Don't worry about pre-mix vs. post mix. Contact Coke and Pepsi. Tell each one that you are evaluating service for a small theatre chain. Ask them what they can do for you. They will tell you what kind of machine will be best for you based on your soda sales at the Colonial. Don't worry about machine costs; each will lease them to you for about $20 per month. Don't worry about where you buy your soda from; all major food suppliers carry both brands. Let them compete for your business. I used to be an unreformed Coke addict. But it seems that it doesn't matter which one you install. If they want a soda, they will buy either. Is there a regional preference in Maine? There are regional preferences in some states. Georgia is a Coke state, Utah is a Pepsi state, and Texans must have Dr. Pepper.
For your tower, just get the basics, cola, diet cola, lemon/lime (7-Up or Sprite) and my favorite, carbonated prune juice beverage (Dr. Pepper or Mr. Pibb.) All other specialty brands you can carry in a display fridge. If the tower has five heads, get two cola heads installed. If it has 6 heads, get two diet cola heads installed as well.
We started out with Coke, Diet Coke, Sprite, Barques Root Beer and Minute Maid Lemonade (0% Fruit Juice.) Then we started carrying Henry Wienhearts Root Beer so wee changed the tap to Dr. Pepper. Then Coke had a cow and offered us national pricing if we carried Mr. Pibb instead, so we switched. It seems most of the staff drink those instead of our customers. Now we make our own fresh squeezed lemonade so we are in the process of dumping Minute Maid Lemonade. We asked Coke about Ginger Ale but they only carry a generic brand for bar guns. This in spite of the fact that they own Schweppes. So we are going to try Diet Sprite in out sixth soda head. Coke says that if you inform your customers that you have Diet Sprite it sells well.
Being a commercial theatre with six heads, I might try starting with Coke, Diet Coke, Sprite, Mr. Pibb and Barques Root Beer. Then I would dump the slow seller and install that second Coke head.
Coke also carries Nestea unsweetened and raspberry ice tea for your soda tower.
But Lemonade and Ice Tea are much better if you make them yourself.
Oh, yea. While your at it, get the Colonial done too.
Damn, there I go again, spewing off at the fingertips.