I would avoid looking for SEO in themes and solely rely on "All In One SEO" plugin, which is effective.
I've used the ugliest, non-SEO themes and have a PR2 on my sites so you can go with what you have heard from somebody else but everything I recommend for Wordpress and SEO have proven results. I got a PR2 on the default Wordpress theme on one of my sites.
I have one very good theme that is very much useful for seo and the theme is designed as per adsense , I GUARANTEE its really good for seo and I also really have some SEO related awesome plugins.. If you PM me, I will provide you them.. Have a gr8 day!
I would not accept themes or plugins from members, but would install them directly from the author or the official Wordpress plugin repository because someone could easily manipulate you into installing a backdoor on your Wordpress account via a PHP shell or something nasty. You were warned.
i think on page SEO is the main SEO technique. if you can do on page properly then start your off page then you can get better result.so i only suggest these. thanks
Instead of looking for SEO Themes I recommend you looking for SEO Plugins like "All In One SEO". The best thing you can do is learn how to apply SEO Techniques and powerful content related to the main theme of your blog or website.
It all depends on several factors, the traffic, the content, the time of day, and if the viewer is interested in checking out what you have to offer e.t.c
It depends on how you want to monetize (make money) with your website. I'm using Socrates and Thesis on several of my hosted blogs and OptimizePress for my capture pages.
There are lot's of themes that are "best". But, I'd suggest you to go with paid themes as they normally are well maintained.