If you consider buying a relatively cheap case for a watercooled setup, albeit an AIO one, I do not thing there is a better option than Fractal Design Arc Midi R2. You will have no problems with memory clearance and frankly with anything else. If you prefer a case with foam on the panels, FD Define R4 is pretty much the same as the Arc Midi R2 when it comes to chassis with a little bit of price premium.