There are 3 positions for installing the drive cages (here in Red, Green and Blue).
You can use the Red and Blue positions at the same time (this is the default installation) but this does pose some limitations. There's not much clearance in the front and it limits your PSU options if you have the rear HDD cage mounted.
Using the middle cage mounting position helps with some of that. You'll have plenty of room for even a large, 200mm power supply as well as enough space for push/pull in the front. However, you do lose 3 drive bays.
So this is something to keep in mind - if you are planning on using the 7000 for all 6 drives 3.5" drives, you'll have to make some compromises. You won't be able to put a radiator in the side and you certainly won't be able to do push/pull in the front.