Thanks for the responses. Definitely understand I should go with 91 or 93. I should have done the math before complaining about the extra cost, but your comment about "walking across to the Honda dealership", while hilarious, is kind of unnecessary. I just didn't realize I'd have to fill premium when buying a 'premium' car. There's also nothing wrong with trying to save money after making a huge purchase.
Out of curiosity, how much can the type of fuel you use lower your car's performance, in terms of mileage, acceleration, etc.?
Is there anything I should do before switching to a higher octane? Or will it not matter, considering I've only filled up 2 or 3 times?