Eventhough the New 3DS XL is more powerful, I still feel like the DS Lite was a more polished system. It's a real shame that it never got an XL variant keeping the GBA slot. You'd have to go on AliExpress and buy an ML shell to give a DS phat the unofficial "DS Lite" treatment, and that's the best we'll ever get I'm afraid.
I have a mid tower as well with a 120mm Noctua, but I think it could fit a 140mm, it's pretty wide for a mid tower. My particular case has 3 spots where a 240mm radiator could fit, so you definitely get more cooling options with liquid cooling, but it is impressive that air cooling works as well as it does. Didn't expect it to beat AIO liquid cooling.