Because I am going to run my Sky+ through an AV amp, I am looking into optical cables, however I'm unsure of how much to spend. Does a Sky+ (and a budget amp - AX640SE) warrant an expensive cable? I don't mind spending a bit if I am garunteed a good sound. Alternatively will a cheapo Cambridge Audio £20 optical cable do the job as good as any other? Same applies for my X-box. Thanks.