I was using 14" Good year tires with my 05 exi and they worked excellent. Then just in the name of looks i went for 17" with very low 205/40/17 and it sucked big time.
Specially on bumpy roads. My suggestion would be to remain within your stock, you'll get the best performance, pick and feeling.
Also keep your alignment right, exi has default alignment problem. I got it corrected after honda guys worked on the front shocks and since then it is perfect.