You can upgrade a regular checking account to a citigold. One person told me no, but she was misinformed, and my Dad's checking account was upgraded keeping the same number and not needing to mess with direct deposits.
The old rules didn't say just one, so I already have a DC card and 3 AA Advantage Cards. I applied for the premium pass card, got my 15,000 bonus miles, and when the fee appeared I called saying the fee should be waived because of citigold and it was. So, don't be afraid to apply for both cards.