Yeah the 600T is a very nice case, I used to have one myself but I replaced it with a CM Cosmos SE. I really like the 450D but the 540 is not my bag.It'll be a while before I part with my 600T, but when I do I'll be looking at ones like the 540.
I would like a couple of fans on the side, to to suck at the two Graphics Cards, plus up to 3 on the front, with good dust filter, to suck cool air in. The two fans on the top can suck the CPU out. One sucking up at the bottom is good too.
I agree the 450D looks pretty good in the photos. Good to see you don't have to buy a black case.The 450D looks like a really nice case.