Terry,
I used to ride (now I'm more of a roadie) and somewhat race Mnt. Bikes and I worked in a bike shop for a year while in graduate school. You CAN spend a small fortune... but I think your best bet is to go to a local bike shop. Find the OWNER and tell him/her exactly what you are looking for and what reasonable price range you want to spend. With bikes, like bows, you often get what you pay for. If you buy garbage made for the big box, it will fail you. Here are a couple of things you want to tell them you want: full suspension, disc breaks, STI gearing by Shimano. If at all possible, I recommend carbon fiber framing. This will cost more, but it will be the last frame for a bike you will ever buy. And it will absorb alot of the shock of the ride, saving you undue fatigue when riding and hunting.
Here are some companies I think make outstanding bikes:
Kona (Hawaii, USA)
Cannondale (CT, USA)
Jamis (Korean as I recall)
Giant (not certain)
Kona specialize in off road bikes and make a pretty serious full suspension ride. Guys who down hill race (that is heading straight down a mountain) ride those. Cannondale can be a bit expensive, but its what I ride and they are super solid, made in USA. Jamis is a good bike, but cheaper as it is foreign made.
Oh, one thing to look for in frame quality, check the welds. The smoother the welds (less beading, dripping, etc...) the better the frame is constructed.
PM me if you have any other questions... I am happy to help!