the only actual leg workout i have of cathes is legs and glutes. it does help the derriere quite a bit. especially if i go heavy on leg presses. and the floor work is a killer.
Gym Style Legs is quite good - plus I think the section in KickMax where she does her blasts is also great. Come to think of it, kickmax is a good one. Cathe really does a great job of focusing on legs in any video that incorporates legs so you really can't go wrong, but I'd say GS Legs is the best for targeting that area