Hi,
all online sitemap generators are using the server which can cause the site slowing down or overuse the memory, CPU. This is why I was not able to use for 2000 products sitemap generator with news, etc... on my server. I tried this:
http://gsitecrawler.com/
This is totally free, can be installed on your computer, not on your server and it connects to your server as a normal webbot. The 8.000 links on my site took about 5 hours to crawl everything. Other php sitemap generators was shut down by the hosting company because of high server loads....
Hopefully it will help people with the same problems I had...