I think it's a VERY good decision to go with something else for the 20x30 print! Trying to force this image into a 4x5 crop that doesn't lose something wasn't going to happen.
As for the photo itself--it's all going to come down to a matter of taste, which is why you are getting such a wide variety of suggestions on the "right" color rendering. Personally, I think you're getting much closer with that last edit. If you could hit somewhere between the last edit and Designer's edit, I think you'd be very pleased with the results.
Also, just something to be aware of and perhaps ASK the printer about before having this printed; sometimes (often with regular prints, but not sure about with a metal print) an actual print of a photo is going to seem a little darker than it does on your monitor. For this reason, I often give a bit of a curves adjustment to my image before having it printed.
So, are you going to crop this to a panorama, 10x20 or something like that?