Sometimes premium themes are the only answer to the added functionality you need or you really need support (you rarely get support with a free theme). Here I list folk I have bought from myself and therefore recommend.
This is another favourite which I have used many times, it offers some good themes at a very reasonable price. You can buy one theme and get access to loads and loads and download and use on as many sites as you like. If you do buy you will not be disappointed but I don’t say that just because I get a commission, i say it because it’s true.
Take a look here ElegantThemes
Although I like free themes from mythemeshop and can I recommend their not so free themes (to be honest I also get a small payment if you link through me and buy a non so free theme) but actually this is not the main reason as I have bought a few myself.
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Theme Junkie Themes offer some impressive themes for a really small cost. There are also some freebies but to get the most out of a theme and of course support, nothing really beats the full versions.
WooThemes offer really good solid themes often if not always with the free WooCommerce plugin well integrated.