I'll have to pass on that for 2 reasons:
1) I have zero knowledge about a brown bess;
2) An amount of money is a vey subjective, mostly personal thing;
My interest happens to be in what a civilian style rifle or smoothbore might have looked like...ie: half stock Hawken styles, full stock Early Virginia style, etc...but that's just me.
PERSONAL ADVICE:
If you'e going to buy something up in that price range or above, guard against rushing your decision as you might regret it later.
Check classifieds, check gun auctions, etc...some good clean used ones show up fairly often.
A $500 choice now would let you jump in, and worst case you could resell it in a year or two for $450-$500 again, after you've settled in to a better idea of what you might like