I've decided to get 420 rad for SV590(thanks for trying it out, btw), but decided to go a little different mounting way:No issues closing the case, had to shorten the tubing run from res to cpu from what is shown in the pictures but all panels line up flush with no bulges. The top panel does not close all the way as the 420mm rad is too tall to allow the power cable to fit through the passthrough. I have not tried the ek pump yet, the Bitspower D5 RGB top will allow the Bitspower Multi-Z 40mm Reservoir to thread directly on and is the smallest D5 pump/res combo out there and should fit no problem, I just haven't gotten around to installing it yet. Tubing goes from Pump >GPU>Rad>CPU>Res. I couldn't tell you what water outlet order is preferable.
1. Turned radiator top to bottom(so fittings are on top)
2. I've used EK Vardars behind radiator and drilled 120 mounting holes in their frames, so it's easy to mount and does not requires sticky tape
As a result - plenty of space to route cables in(even power cable get's in without any issues)
Here's how it looks like:
Mounted rad+fans:
Top cover removed: