Upgrading Joomla, Kunena and CB

I am currently running Joomla 1.5.26, CB 1.4, and Kunena 1.64. I would like to upgrade all of these to the latest versions.
I have tried using jupgrade first, then upgrading Kunena and CB but that was a disaster. So, I am wondering if anyone can tell me the order in which this needs to happen. Can I go ahead and upgrade CB to 1.8 first? Since it integrates with Kunena will it break anything? Should I then upgrade Kunena and if so can I go right to the latest version or do I need to do incremental upgrades? Finally, should I lastly upgrade Joomla?

Also, Kunena forum not much help because I have legacy mode enabled on Joomla. I have no compatibility issues (red "x") but I have even disabled ALL plugins, modules and components (other than CB and Kunena) and if I disable legacy mode it breaks the site. Someone on Kunena forum said it is probably a CB plugin..any thoughts, ideas?

Any help would be greatly appreciated.

Not sure about Kunena.

As far as CB goes you can update to CB 1.8.1 on your existing Joomla 1.5 site first as CB 1.8.1 is Joomla universal and aill work just fine on a Joomla 2.5 site also.

jupgrade works ok with CB and all CB Team plugins installed.

I Make a list of all CB plugins you have - if they are not Joomla 2.5 ready you will have to remove them or update them to latest Joomla 2.5 compatible versions.

Please note that all CB Team released plugins (Advanced, Professional, Developer) are Joomla universal, so your current legacy issues are most likely related to something else you installed.

Sorry not much more I can offer here.