Hi Stacy,
I have Janis Saffell's 'Brand New Butt and More' and find that it provides a really good leg workout, although not all floorwork. It includes standing and floor and she shows you some exercises that incorporate more than one muscle at a time - many of them will help improve your core strength. At first it didn't seem too hard but by the end I was sweating like crazy! If you add ankle weights it makes it much more intense. I also use heavier dumbells than Janis uses. It might be worth a try if you can stand going from Cathe's down-to-earth familiarity to Janis's... well, giggliness.
Btw, I too am a big fan of the floorwork in Karen's GWW.