If you want the RTX 3090Ti or 4090 then I am going to vote with your friend and suggest you get a new case (not necessarily Phanteks). To make your life easier you should also consider a new motherboard, as the Aurora motherboard has much proprietary nonsense. A new motherboard would also open up all of the options for your new CPU . . . and you might as well get a new 1000+ watt PSU. It might sound scary, but if you choose your components wisely, building a new computer is pretty much a snap together Lego kit. Cutting a hole in your chassis is just not a good option.
Basically I am an advanced video editor I grabbed the Aurora R11 a couple years ago with the 2080 super installed and have just capped out on my capabilities as a video editor working on visual effects. Without upgrading my PC completely ( as I am currently running a I9 processor ,64gb ram ,8tb storage with a rtx 2080 super 8gb.) I am looking and ready to upgrade just not sure what will fit inside. I have looked at the size of the 4090 in mm and it seems much bigger than my current 2080. I've read some things on reddit that maybe a fan upgrade would save some space but how would I know what will really fit? My guess is just trial and error? I hope it is possible but the 3090 will have to due worst case. If anyone has any tips or suggestions that would be very helpful. Thanks so much. 
Aurora R11 and RTX 4090. Is it possible?