My favorite is probably
Riordan. I like the look of
Rearden, but the rear thing invites teasing, so
Riordan just avoids that problem.
I'd pronounce
Rearden and
Riordan REER-din, and
Rordan ROHR-din (unless you mean Rórdán, in which case I would say ROHR-dawn... not 100% sure if that's right though).