How to import users and default as email Subscribers

I have just migrated a joomla site over to wordpress – this is the site.

I had many registered subscribers on my joomla site, so i want to import them all into the new wordpress site. I have found a plugin that lets you import users. This is great, but what I want to do is have them all default to be email subscribers.

I have the Subscribe2 plugin, but this will only do it for new subscribers.

I also have it set up on Feedburner but not sure if its possible to integrate between them or which is easier/better to use.

Can anyone please offer me some tips or advice?
Thanks!