I have a 2320 with the same transom as you. I have a 200 Ocean Pro which is a little lighter than the ETEC (my future motor more than likely) you currently have. I also have an 8hp Yamaha kicker motor which weighs about 66lbs. Being completely honest, if I had your newer ETEC I would take off my kicker. So far I haven't needed it but my Ocean Pro is older technology and I don't 100% trust it which is why I keep the kicker on. When I do replace the motor, I'm done with it. Your (and my) boat is not designed for that much weight. I know this because a few times, in snotty weather or backing down on a fish, water has gotten 6" deep on the deck. I love my boat but the transom is just cut too low, definitely wish it was up at least 5". My point being is, yo do not want to add more weight back there and you will actually probably never use the kicker, I haven't.
Lastly, if you were to add a new 15hp ETEC it would add 181lbs to your transom (the 10 is about 100lbs), 3 times what mine weighs.