on my 6th gen accord i went with 17x7.5 lightweight forged wheels. they look great, and at only 14.2lbs each, didn't hinder performance at all. 16-17's and lower are typically used for performance. 18+ is usually considered for show, but what really decides which category the wheel will fall in is weight, and overall wheel diameter. you can have an 18" wheel that will still help your car perform better than a stock 16" wheel. just find a lightweight 18" wheel that weighs the same or less, and make sure you get the correct tire size to compliment the wheel so that your overall wheel diameter isn't any larger than stock. example...my stock 15x6" EX wheels weighed about 15lbs...my stock tire size was 195/60/15...when i upgraded to 17x7.5" wheels, i lost a little weight as they weigh in at only a little over 14lbs...the tire size i went to was 215/45/17...with that wheel and tire combonation, the overall diameter of the wheel wasn't changed, i gained 1.5" in wheel width, and subsequent contact patch, so my car's handling ability increased...i also lost some weight from the stock setup so there were no adverse affects to performance...so with the right wheel and tire combo you can have both looks and performance, it's just not cheap...example...i could have gotten a cheaper set of cast 17" wheels that weighed in at 20+lbs...i would have still gotten the benefits of a wider contact patch, but the extra weight was something i had to avoid at all costs...now i could have gotten a set like that for as cheap as 700 wheels and tires...the combo i went with hit me for 2800 wheels and tires shipped...big price difference, but it was worth it to get the look i wanted, and the performance i needed. good luck picking out your wheels. do some research, and decide exactly what you want from your wheels. But don't forget, if u're willing to pay for it, you can have the best of both worlds.