Yeah sadly I don't think our HK sound system will ever compete with a B & O system. Those are top notch.The Stinger is an awesome car but not necessarily great out of the box. When I first listened to the sound system I really wasn’t impressed at all. However, if you get in there and tweak the settings to your liking it isn’t bad.
My wife has an Expedition with the Bang and Olufsen system and that sounds amazing straight out of the box. Even after adjusting the settings the Stinger doesn’t sound as good but I would still rate it acceptable.
As far as performance goes? Put it in sport mode and use the paddle shifters. If it doesn’t feel fast to you then you need a C8 Corvette or similar. The Stinger is ridiculously fast and has tons of down low torque that you would never get in an Optima.
For gas mileage? This Stinger is actually tremendous..........on the highway............in Eco mode.........with the Coasting feature turned on. The coasting feature disengages the transmission when you aren’t on the gas at all. Once that feature is enabled and activated it helps fuel economy a lot but only if you drive it judiciously.
If you drive it hard it will give you all the performance you should expect. If you don’t drive it hard then it should give you all of the fuel economy you should expect.