When you use sponsor clips, you always have to have a link to the sponsor site (or usually, as per your sponsor's t&c). But that doesn't stop you from linking to other sites as well. I have seen some great implementations where the tube clip and its site banner are in the main section, then in the sidebar or below it are other suggested sites based on the video niche.

BTW, your site looks great, but I would just work on getting better thumbs as a number of them are cropped strangely, cutting off the model's faces.