Top e-publishers for Mystery/Thrillers/Suspense who accept unagented subs?

I've been asked to give a talk in March about writing for the e-publishing market, and though I am e-published in romance I know next to nothing about how it works in the Mystery/Thriller/Suspense world. So, in order to give a light overview I'd like to research the top three or four e-publishers who accept unsolicited, un-agented submissions. I'll then read their submission guidelines and research them on Preds and Eds (if they are on there) and the AW Bewares & Recs forum, but I need a starting point. Thanks for your help!

Thanks, Calla Lily I'l research them. Mystery/thriller/Suspense is the most popular genre for writers in my area, apparently, so I hope I can find something interesting to tell them about the e-pubs for their genre!
Good start to my quest for into, thanks again!

Thanks for the Untreed Reads info. I checked the site and their January 2015 update says they are closed to unsolicited subs, except for agented authors or those already publishing with them.