You do want to be careful about getting a "Coke" system from a store. You may end up paying for it, then find out Coke owns it. They'll take it back. Contact Coke before purchasing, just to make sure they don't own it.
I came across a guy that had a lot of coke products for sale. Contacted him, he stated he had 5 20# CO2 tanks for sale. They were Cokes', so I'm sure the rest of his stuff was leased. I stayed away from that stuff.
Conpewter,
Your Wunder Bar system sounds like the way to go.