Center Channel Height

What is the best location for a center channel. I currently have mine atop my entertainment center angled down 10-15 degrees towards the listener. I am in the market for a new A/V stand and want to purchase something that will allow me to appropriately place the center channel.
If at all possible, make the tweeters of your 3-front speakers(front-left-right-center) on the SAME plain or HEIGHT. This is the most important element in placement of your center channel. Hope it helps.
It's not possible for my current setup, however I will look to accomplish this when selecting a new A/V rack. Thanks for your help.
Most everybody seems to forget the center speaker is a speaker and should be on a stand.On top of the tv or may look better but are not the best choices.You are listening to this speaker just about FULL_TIME This is why the 'big'boys(ritch boys) purachase a third speaker-to match their fronts. So on a stand angled up to reach ear level of where you sit,just as your fronts are reaching you.Use pink noise to dial yourself in. So it is not ear level;it is percieved from your chair ear level