Welcome to muzzleloading! There are a lot of good rifles out there so that is a tough question. If you are looking at long range shooting, I would suggest a modern, scoped muzzy in .50 caliber with a 1 in 28" or 1 in 30" twist. Good news is, many modern muzzys fit this description.
In terms of accuracy, most modern muzzys will shoot very accurately once you find the right load for them.
I believe that it is very important to go and handle the rifles you might buy, and choose one that "fits" you the best. For example, I have handled and shot some muzzys that are high quality rifles, but I just didn't like how they shouldered and felt.
As for brands, I would suggest T/C, Knight or CVA. Most people would consider T/C and Knight to be of higher quality than CVA, but in my opinion some of the new CVA's are very close in quality to TC and Knight. I would go to some stores and handle the following rifles to see which ones you prefer. Listed in random order:
T/C Triumph, Pro Hunter and Omega
Knight Disc and Mountaineer
CVA Accura and Apex
All of these are good quality rifles that have proven to be accurate.