I'm operating from memory here as it has been a long time since I looked at this code. As have been concentrating on monokrom-plasma.
You can have different layers in dxf files and each layer can have tags on it. dxf2gcode know about these layers and uses them for different purposes. I believe you can set feeds/speeds by layer. You could then have your circles in their own layers with an appropriate feed/speeds tag setting.
You might have to dig about in the code and original site for this layer magic but it is there.