The fuse rating is marginal in the XPS2 and it occasionally blows upon being turned on, depending on luck, i.e. the magnitude of the inrush current which varies depending on the precise point in the AC cycle at which you happen to turn it on. Turning if on soon after turning it off also contributes. Have spares available, available from your dealer. (The next higher available fuse rating would have been too high for the XPS2, so Naim chose to go with this).
From the fuse FAQ:
The inrush current *** will depend on the transformer characteristics and the point on the power curve at which connection is made to the AC source. If the transformer core retains any residual magnetism the inrush may well be even more severe.
That said, it happened only once to me and this was when the power cable was not fully inserted and I happened to touch the power cable when messing around with cable dressing. The plug moved in the socket, it arced and blew.
If it blows repeatedly, it indicates a fault in the unit.