Ah, got it. This is an interesting one as I still haven’t found a tableless template platform for Magento. HT hint hint!
The best way to handle this issue altogether is to move your “Add to Cart” button above your image or right under your product title so the other features won’t affect the placement of your add-to-cart button. If you want to do this let me know and I’ll look at modifying the app/design/frontend/default/your_template/template/catalog/product/list.phtml. Perhaps I’ll get around to it in the future, but the fix below should help you in the meantime.
Set the height of the .catalog-listing h5 to fit your longest (highest) title. I’d limit the title length of any item to two lines and set it like this:
Then you’ll need to set your maximum height of your .price-box:
You might also have to adjust the height of the rating and review items, but I don’t have your template and can’t find an example in the demo to work with. I recommend you just plan which features you’re going to use and edit the CSS to limit the height of these items.