I hear the Naim HDX ,(really),not 100% in the best condition.and much more the ARC cd8.Maybe is not true 100% what I will to say,but you may consider this,(lyke a ARC cd3 ovner)....This cd-players about you speack here is categoric in two diferent league.
I must admit ,a source can sound better lyke another in diferent sistems,even this is not so good lyke another,this happened becouse the sinergy of the components,room acustic...
I write this becouse I cannot stay when I read this topic,...in my mind the CD7,8 players is on years of light better like HDX,(I must say the sound of internal hard disk of naim HDX is not usefool compared with the original suport from where was mad the recording,....but he is a good choose to them who have not real CD.SACD,XRCD,K2-HD,...and he have from where take to record this).
BUT!!! We speack here ,when we speack of Audio Research CD8,(I think/hope),of a true high end sistems,not of a recording station.
PS.I really don't whant to undermine the Naim HDX, is a very good cd player/recorder who sound very good,but...in another class lyke CD2....8)