Here is a list of acceptable 16" sizes for Scion XD, according to Discount Tire Co.:
I think the 205/60/16 would look great, it would give the XD more of a mini-SUV appearance. The allowed rim width for that tire size is 5.5"- 7.5", so you are good to go with the factory 16x6"steel wheel.
*EDIT: Some of the sizes listed will require a 16x6.5" or 16x7" rim for proper fitment/performance.
Last edited by XDC; 11-19-2012 at 08:52 PM.