I don't have direct experience with this myself, but the 52/52PS combo has been equated to an 82/SuperCap in performance terms.
This does get a little complicated, though, because as the gear gets to around 10 years old it benefits greatly from a service.
My 52 cost around the £100 mark to service and the 52PS didn't really need anything done, if I remember correctly.
My whole system was serviced at the same time, and was hugely better afterwards.
Budget £200 or so for a service for anything more than eight years old - see the main Naim-Audio website for a list of ages and serial numbers.
cheers, Martin
P.S. you may already be aware, but the 52 head has also undergone some changes over the years as well. I.E. changes are not limited to just the 52PS vs SuperCap.