Hi Samwise,
It is really hard to say what people would offer for it but if you are putting it up on ebay then I would take out the cards that you have doubles for(or x3 or x5!). I think if people were wanting to buy a set for collecting, then they will only want one choir conductor auto or one sirius case topper etc, and what would they want 5 diggory quiddich for

hehe. Seriously though, if you were to go on ebay i think the best bet would be to sell all the extra's seperately and sell this set with only one of each.

hmmm that is just my opinion though and I am not an expert on it at all but that is just what I would like to see as a collector..
Trey