have a look at www.jiliko.net/. The sherpa component is specifically for custom sorting. You need to pay, but it is worth it. Very flexible.

Joomlart K2 filter --> www.joomlart.com/joomla/extensions/ja-k2-search

does what you guys need. I got it, been using it and it's great stuff.

 

 

Also have you thought of adding as tags, all the extra fields you need for sorting? Have the extra fields but also have tags (hide them ofc) for the extra fields you want and then basically use the tags for sorting, which is easy and can be done with many ways and modules. Just an idea.

Andrea Vigato wrote: i use jxFinder that have a basic search with K2 Extra Fields and Categories, then you could improve it by adding some extra code.

jxFinder is not safe anymore.