Is there anyone who owns Mario Kart 8 that won't be buying the DLC?
I was thinking the same thing. Many months after the release I would imagine the game is going to get an influx of people coming back specifically for the DLC. My hope is this results in the vast majority of online players are DLC owners.
My understanding is you would be doing double-duty. If you really are that focused on spending your money to support Giant Bomb I would recommend gifting a yearly membership to friends or some users that you think should get props.