That's a matter of the size of your auditorium. Dolby or DTS shouldn't matter. A couple of drive-in speakers could put out proper levels in a closet, but would hardly be appropriate in a larger room.
Discuss this with your equipment supplier. If you can't get informed answers, post the question (along with room dimensions) here, or on the other popular boards. There are people on either, or both, who know how to calculate the wattage you'll need and what amplifiers and speakers can handle the power.
The physical makeup of your auditorium can have a bearing on the kind of horns the right speaker system should have... especially if you're stadium or have a balcony.
[This message has been edited by rodeojack (edited September 20, 2006).]