From experience, Kayako is a disaster. Horrendous support and a platform that has had only minor upgrades for several years make it an unwise choice.
Perhaps you're right. I don't particularly know that it's the best tool, but the OP could always try it out for themselves:
I believe it is PHP-based as well, if that matters.
The price is pretty good though - ~$500 for an 'owned' license (http://www.kayako.com/purchasing/pricing.php).
All that said, I'm interested to see what other options people suggest.