The YY case is very space efficient. It is a tight fit in the motherboard compartment. It would have been better if they made it an inch longer. There is hardly any space to route the cables from the motherboard compartment to the drive compartment. Check out JSimmons site (I think he is working on it right now):
www.paddedwall.org/watercool/index.html
He has apparently found two versions of the case with different holes to route the cables through. I have the same type as him, only one small hole that is largly covered by the motherboard. On the other side it is obstructed by the 5-1/4" drive frame. If you have to route two watercooling hoses from one side to the other you would have to cut an additional hole. If you want to avoid drilling/cutting completely I don't think this is the case for you. Even with a smaller heatercore you still have to cut out the cardframe.
I tried to fit my heatercore and it fits with no space to spare. I bought a 2-471 core at Autozone (search for 3047169) for $33. It is 9-1/2" x 5-5/8" x 2. With a shroud and 1 inch thick fans on top of that would barely clear the motherboard. No space for a pump left so I have to route the hoses to the other compartment as well...
If you are going for a comercial watercooled case don't get a Koolance. They have really crappy pumps. I blew $350 on one of their first cases. Totally wasted money.
