420mm AiOs are quite rare – not many cases come with space for three 140mm fans in a row – but they’re the biggest size of consumer radiators currently available and offer unmatched cooling potential. Therefore, it may be of interest to you to learn that the Arctic Liquid Freezer II 420 is down to just £79 at Amazon UK, a crazy-low price for a cooler of this size and prowess.
I actually covered the 280mm version of this cooler getting a discount just last week, so let’s let past Will take it away once more:
[This cooler] generally gets strong reviews for its radiator, which offers highly effective cooling. However, the fans that come with the AiO aren’t the best – they can be a little noisier than some other options, so the ultimate setup would pair this radiator with something like a Silent Wings 4 or Noctua NF-A14 for similar cooling potential but with less noise. I wouldn’t recommend picking these up right away though, as depending on your other components and PC positioning the noise very well might not be noticeable.
Otherwise, this is a top choice AiO that performs well and, thanks to this [26%] discount, is in a much lower price bracket than it would be otherwise. Highly recommended, A++++++, would buy again.
So what cases will actually accommodate this? One easy way to find out is to add this 420mm cooler to your cart in PCPartPicker, then see what compatible AiOs are offered by this useful site. Cheap cases that claim to support 420mm radiators (of some thicknesses) include the Deepcool Matrexx 55 V3, the Fractal Design Define S, the MSI MPG Gungnir 100, the Fractal Design Define R5, the Phanteks Enthoo Pro and the Fractal Design Meshify 2. Larger cases, like the Lian Li O11 Dynamic Evo XL, Corsair 7000D Airflow (my case!) and Lian Li Lancool III RGB, also fit the bill. Always double-check though!