The oil filter wrench is the difference between damn-near-impossible to get the stock filter off, and "that wasn't so bad". The $3 price didn't hurt either.
I'm putting one of these (below) on next change. This company even has sizing and adapter cross references specific to the 06 Si.
http://www.fumotovalve.com/
http://www.fumotovalve.com/merchant.cfm?id=127&step=2