Help with digital SLR choices

[Skimmin]

I'm trying to decide on a good middle of the road digital SLR camera. Does anyone have some knowledge to lend? I've been looking at the Canon 50D with a 18-200 lens for the time being a good versatile lens. I've also been looking at the Canon D5 with the same lens. On the Nikon side of things I've been looking at the 90D, D300, and D3(all with the Nikon 18-200 lens). Eventually I will add more lenses no madder which camera I buy, but I believe a 18-200 is sort of a good mix for close up and the entrance to telephoto. They are all in, or below the price range I was expecting but I'm not a professional photographer so I'm not sure if some of the models are overkill for me. I have taken a photoghaphy course so I have a good understanding on how to use them but I also want something I can set to automatic, hand to my girlfriend and know she'll be able to take a good picture too. Does a full frame camera tend to help with quality of enlarging pics? I think these cameras are some decent ones to be looking at, but if you have any other suggestions please feel free to let me know.

Thanks