Welcome back, Matt. The first point is that the term "RCA" strictly speaking refers to the connectors, not the entire cable, so even the "digital coax" cable, which has RCA plugs on the end is an "RCA cable". However, most of the cables which are described as RCA audio have an impedance in the 40-50 ohm area, rather than the 75 ohm impedance which a coaxial cable generally recommended for digital audio use has. The result of the impedance mismatch is that there's additional signal strength loss which if severe enough would make the square waves which form the digital 1s and 0s unreadable. The distance of your cable run of course determines the amount of loss and relatively short runs of "RCA" non-coaxial cable cause no problem. Sometimes 10' is named as a rule-of-thumb safe distance. Another possible consideration is the heavier shielding against interference which coaxial cables generally have, but this shouldn't be a significant factor in most setups.
So, in short(pun intended),your RCAs will probably work fine.
