Paul
I converted an area under a stairwell into a chilled wine room 2 years ago.
I am in Dallas and did not have to worry about temps going under 54 deg. If you are going to do your basement, you migh have to consider a unit that not only cools but also heats so that a even temp will be maitained year round.
If you are constructing a room you must have:
Great insulation
perfect vapor barrier to prevent condensation
exterior door include bottom seal
cooling/heating unit depends on the temp range of your basement
I also used a split cooling system vs an over the door unit as I did not want the noise in the house. in the split system, the compressor is under my house in the crawl space of my pier and beam foundation
I used mahogany wood for my racking as I don't like the "pink" color of cedar or redwood
Gets some estimates and listen to their concerns, you will will learn a lot and get some good ideas
Good luck and enjoy drinking wine at the temp it was intended to be consumed
John