It depends on the standoffs, from what I've seen dell only lets you put standoffs where they have the holes drilled out for them and from what I see the xps 9000 motherboard is standard atx and the 600 cases motherboard only has 5 mounting points for screws. So I would say probably not because the motherboard that came with the 600 case is somewhat unique, and also has a unique heat sink. but your 435t motherboard would fit into any other stranded atx case. So you could get like a 30 dollar case to put it in which would have way better airflow and would also keep your temperatures a lot lower with more room to vent
You are correct with everything. I asked late knowing the worst would be that the case would not work and would need to purchase a case/ps.
Now what kind of pie you got?