Hi,
2nd hand Naim Equipment does tend to hold its price, however be sure to ask if the units have been serviced recently. Pre and Power amps should be serviced approx every 10-12 years.
Get the serial numbers and give Naim a call and they should be able to tell you the history of the units including any servicing.
Be advised however that older Naim amps were only able to be used with Naim Speaker wire. Also make sure the Linn's Phono outputs can be converted to Naim 5pin din as I am not sure if that model has RCA i nputs.