As numerous people have already said, it really, really, honestly, is not the camera that makes the photographer.
First of all, art is a subjective matter, yes, but if to you, art is having a fancy piece of equipment, well..you really are missing the point.
Yeah, no doubt, the higher end camera is gonna help, I never said otherwise, and if you can afford it, then congrats, but it doesn't mean your photos will be better right off the bat. Yes, the quality will be better and if you're making massive billboard sized prints, the quality difference is important. However for normal sized prints (and I use that phrase loosely) You won't see the difference. The thing that WILL make a difference to you is that generally higher end cameras are more convenient to use, (someone already mentioned the two wheel example), and have features that can be really helpful to a photographer.
Manufacturers make entry level cameras so people who are curious about and want to try out something new (like a dSLR) have something to start with that isn't a huge financial commitment. If you can afford to get a more expensive camera, there is no reason not to. There are more things to learn to use, but for me, and I'm assuming many others, learning is half the fun. OP, if you can afford to keep the new camera, and like photography, then keep it! People will say it's the glass that counts, but you already have a fair amount of lenses, and if anything, the new camera will be incentive for you to take more photos.
Also, it's always nice to have a backup body. Especially during an important event like during a wedding.
(oh yeah, mrodgers, if you're ever in the state of Washington, I'd like to put that theory of yours about beating anyone in this forum in a car to the test

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