Thats a stunning Trio you have there! and it's not hard to bring them back to original condition (I've done it). From what I have read about them (and by having owned them I agree) The Stereo 50 is the best of leaks more powefull amps, bettered by the smaller 20. The point one pre is "So So" even after rebuilding. The "Star" in your pile must be the Through Line Tuner! Its an easy refurb just a few caps, The two slide switches and possibly some of those brown resistors in there, unless you are very good you should have it re-aligned by someone who knows about the Throughline! Fit a good decoder to it, mine came from "One thing audio" give it a healthy signal and you will have one of the best stereo FM Tuners ever made, Valve or solid state!
I have sold on the amp and pre-amp (to finance a Radford) but that tuner will never leave me!
Lots of info on the web about this trio, mostly agreeing with me, to be found