I agree that you can probably find room in your case for the pump, but if you want a new case that's larger than a full tower, I recommend the Cogden S101,
http://www.newegg.com/app/viewproduc...+Model%23+S101
This is what I use and it is gargantuan. Comes to 25" tall, 22" deep, and 9 3/4 wide. holds my mobo, 6 hard drives, 3 cd drives, 1 hard drive bay, a floppy, power supply, 4"x4"x5" pump, a radiator air tunnel that takes up about 11"x9"x7". All my hard drives are in 5.25" bays so there's plenty of room between them to breath, and guess what? I still have a 5.25" bay free!