The Atlas baggage is a very nice car. Not easy to find these days though. The MTH 18" one is a nice car as well, again just not easy to find without buying a set of cars. My GGD Amtrak EL-Cap baggage is very accurate, but not one I'm willing to repaint as it goes with the set. The K-Line baggage is also 18" which is the right size for a Phase I-III Amtrak sleeper. I have the full K-Line Phase I set too though so I'm hesitant to repaint it also. I have not seen the Lionel version in person, but I did pickup the dome car and was very surprised at how nice it is. They actually have the closest colors to the Phase I-III colors I have seen and match the official Amtrak color guide fairly closely. The red is not so bright with a hint of orange and the blue is much lighter than the other manufacturers.
I agree on the colors on the MHC cars. MTH has had color matching issues for Amtrak since the beginning. However, that doesn't bother me as much as it does some.
Do you pull your set with MTH F40's? I have a protosounds one, a proto-2 Phase III, and a proto-3 Phase II, but have 4 Phase III versions from K-Line. The K-line version is more accurate for the later built F40s, but the horn is a Leslie A-200. Oh-well. Can't win them all!
It would be fun to see a video of your set running.