So I've decided to keep my bargain-priced Icon! I felt I hadn't given it a fair shake, and was going to try and live with the black level deficiency. What's really saved the day is learning how the Brightness and Color Profile settings in Display settings work.
(pardon me if this has all been covered before, but I don't recall seeing it covered particularly thoroughly in this thread, so I'm offering what has worked for me)
Firstly, out of the box, the Brightness sliders for low, medium and high are staggered. One might assume based on this initial setting that if one were to set all three sliders to the same point, then low, medium and high would result in the same brightness level. This is not how it works. There still is a difference between the three settings even if the slider positions left-to-right are the same. I knew the screen got wonkiest on the medium and high settings, and was almost perfect on the low setting. So what I did was scoot the low slider to the left just a touch, then moved the medium and high sliders to the same respective positions. I now have a screen that even on highest brightness looks very much acceptable, even in a dark room. And it's still perfectly readable in a brightly lit room. I've left it on automatic, so it uses my newly-adjusted three levels PLUS goes even dimmer when in a pitch-black room.
Secondly, regarding the washed out colors I had complained about...I just flipped the color profile to Vivid and that was quite a transformation. Reds became red again. Not sure why I didn't hit this up before...probably just the initial disappointment clouding my judgment.
Anyway, I'm a happy camper now. The phone is fast, fantastic and the size is really just right...and the screen is no longer what I'd call a liability.
Now to get cozy with the camera...more treats await. Thanks for reading!