From my experience with the Rega - and I'm often stereotyped as a big fan of Ü$8 - I'd actually steer you away from the interface that dare not speak its name here.
I've found that a good SPDIF converter is the only way to unlock its full potential. Its best-sounding input is coaxial SPDIF, and it's the only one to accept 24/192.
The cheapest route is definitely optical from the Mac with the cable you initially referenced, but if you want to take a step up sonically, try a few SPDIF converters on a home loan and see which - if any - justify the additional cost. Everyone will have an opinion on this, but the only way to be sure is to try before you buy.