Wouldn't mounting the radiator horizontally, and shrinking the case, force you to remove the divider between the motherboard/drive 'chamber' and the top radiator 'chamber' ? This would force them to share heat, and disrupt the straight-through airflow created with the front and back fan. I rather appreciate the idea of the separate chambers that segregate your heat sources.

I do like the idea of at least cutting the holes in the front of the top chamber to allow 5.25" drives to be mounted up there, because it would allow you to put the (already shallow) fan controllers up there and still keep a quad radiator. Most Fan Controllers I have seen aren't more than an inch or two deep as long as you remove the cd-drive-sized tray they come with. I am not sure of the feasibility of putting the necessary mounting brackets up there for the 5.25" drives though... as they would prevent a quad-rad from ever being installed properly, and block the airflow to the fans. Also this would add even more to the cost of the case... I'd say this is a bit of a toss-up... cost vs more 5.25" bays... I'd still prefer the cheaper case, but I do understand how others would appreciate the bays.