Can I have an evaluation of my CMS System?

This is a long post, so pls. bear with me. To begin with, over 7 years ago, I got trained on the internet by a couple of good mentors who own a web hosting company. I have been using a content management software system called Iwave. I live in Canada, so when I convert the US$ into Canadian dollars, I end up paying almost exactly $500 for them to host 45 websites. They have me on an unlimited site building package, which I haven't used for many, many months. They tell me that I would lose the privledge of Iwave if I moved to another web host. All I use Iwave for is to do the odd update. Most of my sites are filled with older content, so I have been keeping them indexed using various methods including craigslist, yahoo answers etc, to keep the revenue flowing.

I have changed my focus and will not be building any more sites, so want to switch to another hosting company and a big savings. This Iwave system has been excellent, and was built in house by their own programmers and has absolute clean code as well.

My question is can someone recommend a CMS system similar to this one that I can use. I don't want to lose my site rankings, and I am not interested in a huge learning curve should I decide to switch. Here is a link to Iwave. Thanks for your opinions.

http://www.broadwavestudios.com/