You may find this thread useful:

http://www.greenbuildingtalk.com/Forums/tabid/53/view/topic/forumid/22/postid/68519/Default.aspx

Furring over the rigid board works just fine (no need to fill.) Just be sure to allow the sub-grade portion to dry toward the interior by using semi-impermeable XPS semi-permeable EPS. EPS works just fine for the above grade portion too. If going EPS, be sure to use UNFACED eps- foil or poly facers are too vapor-impermeable.

See also:

http://www.buildingscience.com/documents/information-sheets/5-thermal-control/basement-insulation/

http://www.buildingscience.com/documents/information-sheets/5-thermal-control/basement-insulation/files/bscinfo_511_basement_insulation.pdf/attachment_download/attachedFile

You may find these folks a useful resource too:

http://www.insulationdepot.com/

(Don't know how close you are to their TN facility, or if there's one in NC, but it's very cost effective if you're close enough to pick up.)

I use InSoFast, I think it is a great product and is easy to install.