you don't say what your current lenses are ?
if you have EF lenses is it not worth considering full frame ?, if you have EFS lenses i think the choice would be a little more difficult unless you are willing to sacrifice the EFS lenses for the benefits of full frame
the types of photography you mention full frame would compliment perfectly the only question would be cost and the camera of choice at that level has to be the 5d mk3 if buying new
even a second hand 5d mk2 is streets ahead of the 450d in every way it's a fantastic camera with years of life left even though it has been superseded by the mk3
i think we are getting to a stage now where image quality isn't an issue and we hear a lot of people banging on about low noise at high ISO or how accurate the focus is on the latest incarnation of camera bodies and how the older bodies are rubbish compared
how we managed before is a mystery
the reality is not many had a problem with focus i certainly don't with my 5d mk2 or my 50d but i suppose they have to convince the minions they "need" the new features
i have owned the 450d which was upgraded to a 40d and 50d and to be honest they are significantly improved of the 450d in a lot of ways but after that things start to slow down on the improvement side quite a lot
the 7d is still one of the best cropped sensor bodies canon have to offer and is still a very good camera despite the rumors of it's replacement due sometime soon