Dell makes good power supplies.
The problem is the xps 630 is pretty old from around 2008? If you have had it for a while, it might be worth it to get a new PSU although if yours is from like 2010, then I'd still use it.
PS: The case is awesome looking and I know of people who have kept the case and rebuilt using the dell case.
You have a point but there is a saying, "If It Ain't Broken, Don't Fix It"