Note the "Equality Killer" concept comes from Ms Miyuki Misawa's website in 2005. Also players who have visited www.killersudokuonline.com know they publish an "Inequality Killer" every week.
I don't think it would take the players too long to figure out the cage sum. After that it shouldn't be too hard to solve. In the past I've produced puzzles too hard for most to solve and this one is definitely not one of them.
Just for completeness I posted 4 other puzzles in this series elsewhere, available from these links:
http://www.djape.net/sudoku/forum/viewtopic.php?t=1276
http://www.rcbroughton.co.uk/sudoku/forum/viewtopic.php?f=13&t=20
http://www.sudocue.net/forum/viewtopic.php?t=965 (same puzzle as above)
