Since I am new to baking, I have been doctoring box cake mixes BUT I am not getting the height on my cake like I see in you guys' examples for a simple 9inch cake should i use 2 cake mix boxes to get the height i'm looking for or are there additional ingredients i need to add for extra cake batter?

I hope this question makes sense

Not sure how much extra ingredients you are adding to your doctored mixes, but an undoctored cake mix only makes 2x 8" cake pans. If you are not adding more ingredients (flour/sugar, etc.) and now pouring all of that in 9" cake pans, you are not going to get the height. If you read the ingredient list of some of the doctored cake mixes here in the recipe section, it should say what size pan to use. Hope that makes sense.

I use slightly more than one cake mix for two 8" rounds, so I would think a 9" round would definitely need more than one cake mix. Now, I will add that since I converted to a convection oven, I use a little more batter per pan than I needed in my regular oven.

I grease-only-no-flour my pans and they rise higher. I use baking strips around the pans and reduce the temp in the oven.

Here's pics of how they bake higher than the pan: http://forum.cakecentral.com/cake-decorating-ftopic-334013-0.html

Are you wanting to get a two layer cake out of one box? If you are, then yes, I would suggest trying two boxes. Its what I have found works for me when I want a tall cake.

SOme people say they use wasc and add an additional tsp. of baking powder and that raises the cake higher, but I don't make that cake so I have never tried it, although I have been thinking of trying it with the recipe I use most to see if it will make a difference in that one.

I grease-only-no-flour and the batter climbs up the wall of the pan, creating a 'wall of cake'. (see pics in above link)

I cant say enough how great this site is, you guys are sooooooo helpful!!!!!!!!!!!!!!!!!!!!!!