I've used "lftp" for a similar task, it has a command called "mirror", and you can use an option to only transfer newer files. So a command like "mirror --only-newer sourcedir destinationdir" will do what you want. It doesn't have a GUI though, but I liked that, since it was not very difficult to make a little script to automate the job.
I don't know if it's included in the Suse distro, but if it's not, you can get it from the homepage. http://lftp.yar.ru/