J.R.
My kids are 9 & 7 (girls) and 5 & 3 (boys). I am blessed to be able to provide financially for them to have toys that they enjoy--but I'm also thankful that they haven't started asking for things like iPods yet! LOL!
My kids do not know what they are getting until Christmas morning, period. I think that telling your daughter that you got a "cheaper" item before Christmas just ruined her surprise, and threw a bit of water on it as she may not have even noticed the quality issue. You are under no obligation to buy the most expensive product for your child--even if you can afford it. Things like iPods are *extras*, and our children should understand that they should be grateful for not only being provided the necessities in life (food, bed, clothes, lots of love), but especially for extras.
This may sound harsh, but if my kids would be so ungrateful as to complain about not getting the "best and brightest" Christmas present, the item would go right back to the store, to another child who would be more grateful, or at least be taken away from the child long enough for them to reflect on how they should respond to gifts.