We didnt intend to use K2 at first, but ended up using K2 for 99% of our relaunched www.deliciousitaly.com. 

6 months to make, 6 months tweaking.

Need an extension to place modules on a single K2 item. Anyone? 

First Thought -Modules Anywhere

Posted this elsewhere, but have been in touch with KJ of kulendra.net/Joomla-Extensions/modules2pages.html  and his module works a treat in K2.

All it requires is the correct Display Rule for the pre-SEF item and that's it.

So, Yes You Can add a module in a single K2 item (and Joomla article for that matter as well)     

Pure genius and one of the simplest extensions ever.