I kinda figured.
I don't get it though. I understand why you want to filter your products on rpgnow - there's a lot of stuff there and some of it isn't of the best quality. So, if I go to rpgnow, then fine, just show me the good stuff. That makes sense, especially from your PoV. But if I want to search for a product (and I'm talking about the quick search here, since only a small % of people use advanced features), then it should include both sites, since I might be searching on a genre, or author, or whatever - something that crosses the boundry of the two sites.
Or are you really saying that there isn't anything worthwhile on the other site, so there's no real point in searching it anyway?