Homebuyer Tax Credit?

Let me rephrase my question from the last I asked. I purchased my home on 2/7/09, about a couple of weeks before the new bill for the $8000 credit was available to folks who purchased in 2009. A couple of days later I filed my taxes and claimed the $7500 credit prior to the bill being signed into law. Now I understand that I am able to claim both since my purchase was before the bill was signed into law prior to the old credit being eliminated. I am not going to amend my 2008 taxes, but claim the new credit on my 2009 taxes. My question is instead of off-setting the old credit with the new credit to receive the $500, can I just opt to take the full $8000? Or is it mandatory that the off-set takes place?