Pro-Support, the one I worked in is nice. You'll get top notch American based support for optiplexes or vostros. They won't be able to help much with software issues except for windows or ms-office issues since it's business based, but anything hardware related they can help with.
You can even upgrade yourself although they won't warranty the parts you put in it or any damage you do to the unit installing something. It doesn't void your warranty to install 3rd party parts, though, say an SSD.