Well it really depends on your needs there are about 10 really high quality wordpress theme clubs, woothemes is one of the best but I enjoy themeforest...
I prefer to design a site for a client rather than picking one from the theme places, My clients typically like a unique theme, and have control over how their site is designed aesthetically. Our themes are SEO friendly, we also provide an SEO Tuneup for you when you hire us for design. :-P