I'll be getting the TT-PSU at some point for sure - however following purchase of Naim 112/150, I'm probably going to go for a Naim Stageline as it seems to be superior to the Fono by all accounts - and within budget second-hand =)
I picked up a Stageline from a dealer for well under £200 and if you are going down the Naim amp route the Stageline may well be the way to go, the added cost of the i-supply may not be cost effective otherwise . You must do the TT-PSU upgrade as this is a very inexpensive upgrade for the gain in performance.