I've not read the whole thread, only skimmed but....
It sounds like you don't need the 5D mkII due to not knowing what it fully offers and not being 100% sure on your shooting style.
I certainly would not swap my 40D for a 5D mkX, heck the 1Ds I used the past week would not even sway me away from my 40D, with 7.8FPS it's too valuable an action shooter and fast at everything it does.
I'd have to keep the 40D and buy another body for FF/Movies etc.
A 5D won't help your photography, it will make you feel better for a short while but it won't get you better pictures.
I suggest practising your photography until you're fully confident in your own style and requirements