I think it'd be best if the reply box was at the bottom. A lot of forums do it this way and people are kinda use to that. It seems very strange to have it @ the top. Plus @ the top people are more apt to respond w/o having read the thread. By placing it at the bottom at least they have to skim down a bit before they reply.
Yeah I know what you mean most forums are like that and it makes it much more easier to navigate. I Told my buddies about this site so I think they will surely enjoy.I know I do.