Air conditioning a home theater.

I have converted my den into a dedicated home theater and listening room. It is posted on Audiogon's Member Systems under Home Theater, Marc's Media Room Madness. The room is great but, since the warmer weather started, we discovered that our home's central air conditioning system is inadequate for cooling that room. Perhaps enclosing the previously open entrance to the room and the addition of carpeting and black out curtains is retaining heat more than before. There are various solutions. The two we are considering are to turn our central system into a zone system or install a "mini split" system. I would appreciate hearing from anyone who can weigh in on which system is more efficient and, most importantly, which one is quieter. Thanks.