In some respects your system is similar to mine, Mikeandvan. I have Junior Spacedeck (same platter as Spacedeck I believe), [Also Modified Lenco 75], Ace arm, Nag 200, Graham Slee Elevator, Slee Jazz club, Quad 66 pre, Quad 306 power into Kef 1042s.
As I said in previous post I have a definite improvement in sound quality with the Speed box so am not surprised you are hearing more good things.
Enjoy!