I'm guessing here but I would say yes.  If your deadset on doing the mod you could prob keep your warrenty by purchasing a replacement side panel and doing the mod on that.  Dell Spare Parts might be able to help you out with a P/N for the side panel.  Or Chris_M might.

Lonewolf_NW08,

Sadly, we do not have a part number for the side of the chassis.

You might keep an eye on ebay for that side panel.  I have seen a few of these for the XPS 720.  It is only a matter of time before one shows up for the 630.  That sounds like a fun project.  I am not sure that it should void the warranty since it doesn't change any of the hardware, but it is a nice excuse Dell could use if something ever did go wrong.  I would agree that a replacement side panel would be the way to go if you can find one.

@CHRIS_M:  What about a P/N for just the whole Chassis? 

Might be something worth bringing up to the Parts Divison..... 

Lonewolf_NW08,

Nope.