The BEST aftermarket is sold by K5optimastore.com the canbus unit is amazing. Bought it and installed it on my 18' sxl. It works wonderfully and I wouldn't trade it for any other.
Thank you!It has features tailored to the optima that you can't match.
Auto unlock/lock of doors as you walk away/to the car. Sunroof opening/closing for the hot days. Unlocking your car without keys. My favorite feature.