The height of the speakers off the floor will greatly affect the bass. If the distance is too large, you will lose quite of bit of bass depth. I had to play around with this for a while to get things dialed in correctly, and in my room, it seems about 3/8" worked best for me. I have them tipped slightly up -- that really solidifies the imaging. Morganc is right on (I actually bought his upgraded Omen Defs) -- they sound very good placed just about anywhere, but they can sound fantastic when you find the right placement.
My new ZU Omen Def's arrived
In Sangria red. I hooked these up to my Elite receiver and using 10 year old Monster (don't laugh) 10 AWG cables. I'm amazed how well these things sound out of the box. They image like crazy. Very smooth and very revealing. I'm still experimenting with placement since I do not have a natural listening sweetspot. The bass is outstanding and very clear. Low listening levels sound fantastic. Actually, the Pioneer Elite receiver sounds very good (to my ears). Since business is great this year, lots of money going into a future house and a little fun money will be saving up for a Decware Zen Torii. I hear the Decware's and Zu's are a good combination.