You cannot place one auction on 2 sites. Whoever bids less on other forum, what you are going to do about it? Refuse him? Or sell domain to both?
EDIT: Reedit your post, and appologize to users, for not mentioning you are selling this on 2 places at once. And seriously, what would happen if on DP thread someone offers you more? Who would you refuse, not to sell him?