By "upgrade" I meant sell the FT-450 and buy the FT-450D instead ...
I have an ancient Kenwood AT-130 manual ATU which tunes the G5RV very well, but an internal tuner might be useful for other antennas. I do some (but not much) CW work so the extra filter might be beneficial. All-in-all, it's hard to justify the price difference. I was hoping someone would say it was a very worthwhile upgrade and I would then feel justified in spending the money
I agree with you - it's hard to justify the price difference between what you have, and what you'd need to spend to replace it with an FT-450D.
A real "upgrade" would mean a Yaesu FT-950, or Kenwood TS-590, or something else in that $1500 price range. Even more money, but a genuine improvement in capability.