I do not know if this is possible for you to do, but If you could also display how much btc is on buy orders, for that coin at the price used to calculate profitability.  If a coins first few bids are much higher than the next and is only for .0001 btc that makes a huge difference in your profitability.  You would also be the first coin profitability site that I know of to implement this.  Another option, might be an average of buys vs rates, there might be even more ways to help calculate this.  I am not really a math person I just know all to well from following some calculators in the past that you can waste many hours of mining and end up with a profit well below that listed on the site.