So I have a 2015 Optima with the UVO system. The stereo system is rather lacking, but I want to upgrade speakers and add a subwoofer possibly while keeping the factory head unit with the UVO system as I have a back up camera and everything with it as well. I have searched these forums and found a few peoples systems. Now what I am wondering is what speakers you went with, which coverters, what subwoofers and amps, and cost involved in all this? Also what did it cost you to do it yourself vs having it installed? Thanks in advance. One of my local installers said don't even bother unless I upgrade to an aftermarket deck as the sound difference would barely be noticeable. I find that hard to believe. Hoping people on here will prove him wrong.