Gravity & Grace by Peter Sterios. Very challenging but I haven't done it very much since it's such a long practice. Aside from the main practice, there is a hip opening flow and a backbend flow.
Also, Mark Blanchard's Sedona series is very challenging. I don't really like his personality but I do it when I want a tough practice. There are 5 DVDs in this set - The Foundation, The Flow, The Core, The Culmination and the Stretch. I've done all of them except for The Stretch. The Foundation has a tough standing series which lasts about an hour and then there is 25 mins. of floorwork. My legs were burning - I couldn't wait to get down to the floor.
Both of these have headstands and handstands. Mark does lots of chaturangas, standing splits.
Eoin is probably my favorite - I have both Power Yoga for Happiness 1 and 2 and they are both worth getting. PY4H1 has 5 practices and PY4H2 has 7 (there is an 85 mins. full practice and then 6 premixes). Eoin doesn't do headstands or handstands but he likes to do bound poses.
Marcy