To me this is a solution in search of a problem BUT there is some opportunity as there are certainly problems with the other sites:
Filter by genetics - you could input the morph list from WOBP and have people select genes as they post animals - filter by included gene
Filter by cost
Follow or Block individual sellers
Would be cool to incorporate seller feedback right on the page - some kind of star rating system with comments
You could really leverage some kind of price benchmarking system there - save the cost and morph of anything sold via Buy It Now and open the database public
I mention all of these because it looks like there is an attempt at merging all of the elements into one seamless experience - browse, buy, ship all from the same place at the same time with a nice clean record of each stage of the transaction. Looking forward to seeing the site develop!