Yes avoid the XPS route
You might want to try the building and upgrading forum and check with them first.
If nothing else that money will buy you a much faster, more upgradable, and more specific PC for the task.
If you do get a standard Dell, that's fine, but don't "upgrade" through Dell, its one of the greatest ripoffs known to man!..
just buy an aftermarket graphics card and slot it in yourself (very easy with youtube)
Here are two that will play minecraft, and will run with the Dell's 300 watt power supply and cost 50/60 euros