Looking to cool a 1080ti and 8700k silent operation is the main priority adding a 120mm rad at the back would be ok right?
Definitely not enough to cool with a single 240mm. The general thumb rule is a 240mm for cpu or 1 gpu only then add another 120mm per component added.
So minimum you would require is at least a 360mm rad. Can be 240mm + 120mm or tripple 120mm or a single 360mm rad.
But my advice to you would be, add as much rad as possible if you can. Hence you can get away with much lower rpms fans.
There are a few good cases around.
- Thermaltake Core P5 (open bench style, may accumulate dust)
- Lian Li PC-O11 (clean looks with dual chamber style, mainly aluminium)
- Cooler Master Mastercase H500p (mainly steel)
- Inwin 805 (nice construction with plenty of rad support)
- Inwin 305 (Cheap but mainly made out of steel)
- Corsair 750D airflow (Very old dated case with no TG, but still the best practical case for water cooling)
- Corsair 900D (Big spacious and great rad support, very big, and mainly steel construction but it will be better if you have lots of components to cool)
- Fractal Design S (Cheap mainstream case, mainly steel with standard rad support)