tangor - 11:45 pm on Jul 19, 2010 (gmt 0)
The quick and "humorous" answer is "hire somebody". As for "clean and beautiful" your CONTENT and PURPOSE dictate the appearance. Look at any requirements for site operation to determine if VISUAL or TEXTUAL is needed. Most ecommerce sites have little need to be the latest photo/art gallery with fancy borders, animations, or "pretty." News or Educational or Information sites lean toward readable text presented in easy to view formats.
Once one reaches the need to automate page generation, or some part of the page content (php, database, commerce/products) SOME of the potential visual "beauty" is traded off to achieve that efficiency.
There is no ONE best "clean and beautiful" except for clean code beautifully delivered to the browser with few to no validation errors! AND has SEO friendly URI from the very start.