I don't understand the concept of best rate? your website might tell us the latest sold price but in reality you can even place and order cheaper than price wand wait for the trade order to get execute. 
The concept of best rate to give an information about the best rate for people to buy or sell his coin. This is only an informative site and i think this site doesn't connect use API to be able to trade on the exchange site at the same time. I have seen OP has also provided some tools too. OP, i like that coz it's clean and simple honesty it looks like you just need to add more coins on the list
Thx, can you tell me which currencies and brokerages you would like to see on the website?