I know the area, but more from a fishing standpoint than for hunting.
However, Madison County (MT) ranks as one of the premier hunting areas in the US and Ennis sits in the heart of it.
If it were me, I'd look at outfitters all along the Madison Range, extending from Ennis to West Yellowstone (a distance of 70 some miles).
Get yourself in shape, you could be hunting between 5-10,000' in elevation. Archery season starts in September, and the weather conditions at those elevations can change in a heartbeat. I think you'd love every minute of it.