I am looking for a good stock photo source for my clients

I have been thinking about purchasing a membership to a stock photography site. I stumbled across a plugin called Microstock Photo Plugin. It uses Fotolia or iStockPhoto to automatically purchase the photo and license to use the photo on a website. I am looking for some insight if anyone has used this plugin before. I am also open to referrals to sites that do not have a wordpress plugin. I just need a good value for photos and would be nice to mark them up a little too when I sell them to clients...