Create Custom Wordpress Theme/Functionality

Hello, I am looking for help in creating a website based on wordpress. The functionality I am looking for can be found in other wordpress themes, but none combine the features in the way I need. The website requires the following core components: 1) Allow registered users to submit Coupons like Retailmenot.com. 2) Allow users to vote on coupons and comment on them like [login to view URL] 3) Allow users to submit questions like yahoo answers 4) Allow users to vote on the best answer to questions like yahoo answers 5) Allow registered users to submit stories, which are just wordpress blog posts. Almost all of the content on the site is user generated from user submitted coupons, questions,answers, stories and comments. I am looking for a very easy to customize theme, I need to be able to easily replace graphics, colors, etc. The site is rather simple in design, so I really want the graphics to look nice. Please take a look at the attached mockup and let me know if you can help me out! Thanks!