crimson-pc12 :
itzdanielp :
The Apollo will not fit it without removing the HDD bay, which is attached with rivets. Not an easy removal.
The Guardian 921 will fit, but it is tight.
Does the removal of the HDD bay affect the computer at all? I'm new to PC building.
Only if you're installing a RAID array, which I would bet you are not.
However, if, like itzanielp said, the HDD bay is riveted in on the Apollo, you might tear the case up getting it out. I would recommend the Guardian 921.