First try an RCA cable from the Pro Plus, then its optical and coax output into your amp and decide what you like best - it's entirely subjective as we all have different amps, DACs, speakers, room acoustics, preferences and ears/brains...
Edit: I'd also advise not to get caught up in the almost inevitable coax v. optical, more expensive "better" cable discussions - many find the supplied optical cable, for example, to be perfectly capable and adequate for their needs, while others may try to persuade you otherwise. Hic sunt dracones...