The reply above is spot on. Paying £300 for it could be considered an incentive to service it and bring it back to full glory as your total outlay will still be a fraction of a new XS3, which is its nearest competitor.
I have two Nait 5, one in my main system and another in my office system and they both sound lovely, better if fact than many other Nait’s that have gone before in this house, including the NaiXS and to a degree a SN2. One of mine has been back to Naim for a full rebuild and updated volume pot, the other untouched. It’s probably the best value for money Naim amp out there considering they go for similar money to a 5i, and it’s by far a superior amp. I run both mine with Naim psu’s, one Hicap2 and one FC2, but they sound superb standalone and that’s how i used them for a long time.